US 20100227876A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2010/0227876 A1 Rech (43) Pub. Date: Sep. 9, 2010

(54) METHODS OF REDUCING SIDE EFFECTS Publication Classi?cation OF ANALGESICS (51) Int CL A61K 31/485 (2006.01) A61K 31/40 (2006.01) (75) Inventor: Richard H. Rech, Okemos, MI A61K 31/445 (2006-01) (Us) A61K 31/439 (2006.01) (52) US. Cl...... 514/282; 514/409; 514/329 (57) ABSTRACT Correspondence Address: The invention provides for compositions and methods of MARSHALL, GERSTEIN & BORUN LLP reducing pain in a subject by administering a combination of 233 SOUTH WACKER DRIVE, 6300 WILLIS mu-opioid receptor agonist, kappal-opioid receptor agonist TOWER and a nonselective opioid receptor antagonist in amounts CHICAGO, IL 60606-6357 (US) effective to reduce pain and ameliorate an adverse side effect of treatment combining opioid-receptor agonists. The inven tion also provides for methods of enhancing an analgesic effect of treatment With an opioid-receptor agonist in a sub (73) Assignee: RECHFENSEN LLP, RidgeWood, ject suffering from pain While reducing an adverse side effect NJ (US) of the treatment. The invention also provides for methods of reducing the hyperalgesic effect of treatment With an opioid receptor agonist in a subject suffering from pain While reduc ing an adverse side effect of the treatment. The invention (21) Appl. No.: 12/399,629 further provides for methods of promoting the additive anal gesia of pain treatment With an opioid-receptor agonist in a subject in need While reducing an adverse side effect of the (22) Filed: Mar. 6, 2009 treatment. Patent Application Publication Sep. 9, 2010 Sheet 1 0f 4 US 2010/0227876 A1

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METHODS OF REDUCING SIDE EFFECTS (1996), Briggs et al. Pharmacol. Biochem. Behav. 60: 467-72 OF ANALGESICS (1998). Briggs et al., Pharmacol. Biochem. Behav. 60: 467-72 (1998) also demonstrated selective antagonism of mu-opioid FIELD OF INVENTION receptor antinociception by beta-funaltrexamine ([3-FNA) [0001] The invention provides for compositions of opioid and selective antagonism of kappa-opioid receptor antinoci receptor agonists and opioid-receptor antagonists and meth ception by nor-binaltorphamine (n-BNI) in the CWTF model. ods for reducing pain in subjects. [0006] Additive or enhanced pain relief, With reduced side effects produced by combining agonists, Were also observed BACKGROUND by Verborgh et al., Acla. Anaesthesiol. Scand. 41: 895-902 (1997).; Sutters et al., Brain Res. 530: 290-4 (1990); and Ross [0002] In attempts to develop analgesics devoid of mu et al., Pain. 84: 421-8 (2000), among others. Bie et al., J. opioid receptor type tolerance, dependence, opioid-induced Neurosci. 23: 7262-8 (2003), on the other hand, reported hyperalgesia (OIH), and addiction lability, kappa-opioid potent antagonism of mu-opioid receptor agonist analgesia receptor agonists Were developed (Walker et al., Psychophar by kappa-opioid receptor agonists With acute dosing targeted macology. 155: 362-71 (2001); Wadenberg, CNS Drug Rev. at the brainstem nucleus raphe magnus. But they also shoWed 9(2):187-98, 2003)). PentaZocine, the ?rst kappa-opioid receptor agonist marketed (a mixed agonist, With mu-opioid that kappa-opioid receptor agonists reversed the hyperalgesia receptor activity) had little effect on respiratory function, induced by chronic mu-opioid receptor agonist activation. limited analgesic ef?cacy and loW dependence/addiction Thus, the interactions of these agonists differed on the basis of liability. But as a partical mixed agonist pentaZocine also had acute and chronic treatment. They also appear to differ on the modest e?icacy at kappa1-and kappa2-receptors. Unpleasant basis of single-site application versus diffuse application, as side effects of anxiety, dysphoria, and psychotomimetic With systemic administrations or mixed administrations of actions hindered patient acceptance. mu-opioid receptor agonists microinj ected into brain sites [0003] Henck et al. (Pharmacol Biochem Behav. 18(1):41 and kappa agonists applied to spinal sites by intrathecal injec 5.1983)) studied a congener, cyclaZocine, reporting a behav tion (MiaskoWski et al., Brain Res. 608: 87-94 (1993). ioral spectrum in rats similar to the hallucinogens lysergic [0007] The Work of Yaksh (Acla. Anaesthesiol. Scand. 41: acid diethylamide (LSD), 1-(2,5-Dimethoxy-4-methylphe 94-111 (1997)) relates in large part to concepts of visceral nyl)-2-aminopropane (DOM), mescaline, and dimethyl pain and opioid actions on visceral receptors. Yaksh used tryptamine (DMT), and these actions are mediated via brain microinjections of drugs into supra-spinal (brain) and spinal 5-HT-2 agonist activity. Additional kappa-opioid receptor sites to test effects on chemical, mechanical, or high-level agonists Were shortly introduced: butorphanol (mixed partial thermal nociceptive stimuli. These antinociceptive insults agonist at kappa1-, kappa2-, and mu-opioid receptors) and preferentially activate visceral pain. Yaksh and colleagues nalbuphine (kappa1-, kappa2-receptor agonist and mu-opioid formulated theories of complex pain pathWays and drug receptor antagonist), With pentaZocine-like side effects. Nev actions still extant today. This Work proposes that ascending ertheless, butorphanol has had more success for pain relief in and descending neuronal circuits connect to brain stem hubs human and veterinary medicine than pentaZocine, perhaps (periaqueductal gray (PAG), mu-opioid receptors; rostral relating to the more de?nitive mixed agonist ef?cacies. ventral medulla, mu/delta-opioid receptors; substantia nigra, [0004] A host of research studies have demonstrated mu-opioid receptors) and to the spinal and dorsal-horn junc prominent antinociceptive effects of kappa-opioid receptor tions (mu-/delta-/kappa-opioid receptors). Yaksh described agonists over the last three decades, particularly for the ary these pathWays and junctions as integrating and modulating lacetamide class (U-50,488H, enadoline, spiradoline, U-69, nociceptive and antinociceptive impulses and greatly eluci 593). Using the colorectal distension assay (CRD, a model of dated the concepts of mechanisms of pain perception and visceral pain) in dogs, SaWyer et al. (Amer. Vet. Res. J. 52: analgesic drug actions. 1826-30 (1 991)) reported enhanced antinociception by butor [0008] Use of combinations of mu- and kappa-opioid phanol When combined With oxymorphone or ketamine. Ket receptor agonists has been proposed to improve therapy of amine attenuates acute mu-opioid tolerance by antagonizing chronic clinical pain (Smith, Pain Physician. 11: 201-14 NMDA activity and thus inhibits emergence of endogenous (2008)). This hypothesis portended separate antinociceptive excitatory opioid receptor systems, decreasing their activa drug actions on junctions in parallel- or serially-connected tion of pain-facilitatory systems (Fundytus, CNS Drugs. 15: neuronal chains in pain-related central nervous regions as 29-85 (2001)). Briggs et al. (Vet. Surg. 27: 466-72 (1998)) affecting synergistic analgesic interactions. Chronic visceral combined oxymorphone and butorphanol in cats tested in pain, more often prevalent in severe clinical cases than is CRD to enhance antinociception and reduce side effects, as somatic and cutaneous pain, is also more dif?cult to manage had been noted in dogs by Houghton et al., Proc. Soc. Exp. (Joshi et al., Curl: Rev. Pain. 4: 499-506 (2000). This rela Biol. Med. 197: 290-6 (1991). tionship related to Smith’s hypothesis, since visceral pain is [0005] Side effects of mu-opioid receptor agonists (eupho relieved consistently With mu- or kappa-opioid receptor ago ria, constipation, enuresis, pruritus) are often mirror images nists alone or in combination (Ness et al., Pain. 41: 167-234 of those of kappa-opioid receptor agonists (dysphoria, minor (1990); von Voigtlander et al., .1. Pharmacol. Exp. Ther. 246: gastrointestinal effects, diuresis, anti-pruritus) in a variety of 259-62 (1988); MiaskoWski et al. Brain Res. 608: 87-94 mammalian species (Pasternak et al., Life Sci. 138: 1889-98 (1993), Briggs et al., Pharmacol. Biochem. Behav. 60: 467-72 (1986). Thus, the combination of mu- and kappa-opioid (1998)). Also of interest in this sphere is the large number of receptor agonists tends to reciprocally reduce each agonists’ arylacetamide kappa-opioid agonist class of drugs demon side effects, While producing additive antinociception in the strating selective, highly ef?cacious, and full-range of anti cold-Water tail-?ick assay (CWTF). Briggs, Interactions of nociceptive effects (see Briggs et al. Pharmacol Biochem mu and kappa opioid agonists. Ph.D. Thesis Dissertation Behav. 60: 467-72, 1998)). US 2010/0227876 A1 Sep. 9, 2010

[0009] Morphine and other mu-opioidreceptor agonists are administration of the combination of three opioid classes of not suitable as analgesics in feline species because they pro drugs: (1) A mu-opioid receptor agonist (e.g. fentanyl, oxy duce manic excitation. This result is due to the fact that the morphone) at a moderate dose level such as the ED-50 dose or nervous systems of cats contain dominant excitatory mu less; (2) a kappa-opioid receptor agonist (e.g. spiradoline, opioid receptors, Whereas in humans, monkeys and dogs the enadoline, U69593) at a moderate dose level such as the inhibitory opioid systems are dominant. Therefore SaWyer et ED-50 dose or less; (3) a nonselective opioid receptor antago al. (J. Amer. Hosp. Assoc. 23: 438-46 (1987)) tested butor nist (e.g. naloxone, naltrexone) at an ultra-loW dose level phanol for analgesic activity in domestic cats against experi (such as a nanogram dose level) that suppresses tolerance and mental visceral pain induced by the colorectal distension dependence development in both classes of agonists. The assay (CRD). Effective antinociception Was obtained, the cats combined agonists afford additive or synergistic analgesia, initially shoWing calmness, purring, and kneading. But as the depending on the type of pain involved, and greater pain relief analgesic response Waned, the animals became someWhat at loWer dose levels than When the agonists are administered irritable. These results suggested that the initial drug response singly. The incidence and intensity of adverse side effects are re?ected both mu- and kappa-opioid receptor analgesic less by virtue of the loWer agonist dose levels, as Well as by effects, While the later responses, as the mu-opioid receptor interactions of the opposing spectra of agonists’ side effects. agonism declined, re?ected unopposed kappa-opioid recep For treating acute short-duration pain, the combined agonists tor agonistic effects. only may suf?ce. HoWever, cases of repeating subacute or [0010] Sawyer et al. (Amer. Vet. Res. J. 52: 1826-30 (1991)) chronic persistent pain require inclusion of the loW-dose and Houghton et al. (Proc. Soc. Exp. Biol. Med. 197: 290-6 antagonist to maintain analgesia With loW doses of both ago (1991)) also studied butorphanol analgesia against CRD in nists and to avoid development of both mu- and kappa-opioid dogs. Effective analgesia Was produced and Was enhanced by receptor tolerance and opioid-induced hyperalgesia. addition of oxymorphone (mu-opioid receptor agonist), With [0014] While the most dramatic potentiation of analgesia reduced respiratory depression relative to the degree of oxy by applying these methods derives from combining the mu morphone respiratory depression When oxymorphone Was opioid receptor agonist and ultra-loW doses of antagonist, administered alone. other bene?cial interactions of the three combined agents can [0011] Studies using combinations of fentanyl (mu-opioid be achieved. The tolerance and dependence folloWing com receptor agonist) and enadoline or spirodoline antinocicep bined chronic dosing With the kappa-opioid receptor agonist tive doses Were performed in place preference (PP) vs. place Will also be suppressed by including the opioid receptor aversion (PA) conditioning procedures in rats (Briggs, Inter antagonist, resulting in persistent and prolonged analgesia actions of mu and kappa opioid agonists. Ph.D. Thesis Dis induced by the kappa-opioid receptor agonist. Interactions sertation (1996); Briggs et al., Pharmacol. Biochem. Behav. betWeen chronic doses of mu-opioid and kappa-opioid recep 60: 467-72 (1998)). The conditioned place preference of fen tor agonists further attenuate tolerance and dependence tanyl in a X-maZe or a black-White tWo compartment maZe development for both agonist classes. Was attenuated by combinations With enadoline or spirado [0015] Activation of excitatory mu-opioid systems by line. Of special interest Was the ?nding that training and chronic dosing With a mu-opioid agonist involves, at least in testing of subj ects With spiradoline shoWed signi?cant dose part, mobilization of endogenous excitatory amino acid sys related PA that Was attenuated When the drug Was combined tems (EAA, NMDA, glutamate) as an intermediary. Thus, With fentanyl. dextromethorphan and ketamine, NMDA antagonists, rein [0012] Treatment of chronic pain With mu- or kappa-opioid state the analgesia of chronic mu-opioid agonists. Less is agonist leads to development of tolerance and dependence, in knoWn about the details of tolerance and dependence of large measure by activation of endogenous excitatory opioid chronically administered kappa-opioid agonists. Gender dif systems. Mu-opioid agonists in particular promote opioid ferences occur in humans to the analgesic ef?cacy of nalbu induced hyperalgesia (OIH). Both kappa-opioid agonists and phine on repeated dosing after dental surgery (Gear et al., J ultra-loW doses of nonselective antagonists (naloxone, naltr Pain. April; 9(4):337-41 2008). Females experienced pain exone) suppress mu-opioidreceptor agonist induced OIH and relief, While males reacted to the same doses With increased dependence characteristics, reinstating and prolonging the pain. Combining nalbuphine and a sub-analgesic dose of analgesia of loW doses of mu-opioid agonists. The ultra-loW morphine in males reversed the anti-analgesic action of nal antagonist doses block activation of excitatory opioid sys buphine. These authors had previously enhanced and pro tems but do not affect the activation of inhibitory opioid longed nalbuphine analgesia by combining the agonist With systems. Furthermore, the addiction liability of mu-opioid very loW doses of opioid receptor antagonists, the interaction agonists (reWard effect) is suppressed by the opposing mood being sensitive to a critical dose ratio. effect (aversion) of kappa-opioid agonists. The combination [0016] The order of administration of the three drug com With kappa-opioid agonists plus ultra-loW dose antagonists ponents of the invention is not highly critical. It may be also reduces tolerance and dependence of the mu-opioid ago simultaneous or separated by time periods short enough to nists, thereby enhancing analgesia and decreasing compul alloW for overlapping effects. Referring to routes of admin sive mu-opioid agonist abuse. Therefore, there is a need to istration, oral, intravenous, intramuscular, subcutaneous, develop pain management treatments and opioid receptor sublingual, intrathecal, or transdermal appear acceptable for agonist/antagonist compositions that effectively reduce or most of the candidate opioid drugs Which Would be used. suppress pain While the emergence of the adverse side effects is also reduced. [0017] The compositions, methods, and utility of the inven tion are directed toWard the reduction, amelioration, or sup SUMMARY OF INVENTION pression of pain in the broadest sense. That is, the intent is to treat all types of pain, including short-term, long term, inter [0013] The invention provides for methods of reducing mittent or persistent, somatic pain, visceral pain, and neuro pain and adverse side effects in a subject comprising the pathic pain. The invention provides for compositions, uses US 2010/0227876 A1 Sep. 9, 2010

and methods of administering combined opioid receptor ago agonist are administered as a single composition and the nists (mu- and kappal-opioid receptor agonists) and a non nonselective opioid receptor antagonist is administered as a selective opioid antagonist to reduce pain in a subject, separate composition simultaneously or Within a short time Wherein the subject may be any mammalian species, includ frame before or after the opioid receptor agonists. In some ing humans. variations of the method or uses of the invention, the doses of [0018] The invention provides for methods of treating pain a selective mu-opioid receptor agonist and a selective kappal - in a subject, the method comprising administering to a subject opioid receptor agonist are administered in one composition. suffering from pain, a moderate dose of a selective mu-opioid In addition, in some variations of the methods or uses of the receptor agonist, a moderate dose of a selective kappal - invention, the doses of a selective mu-opioidreceptor agonist, opioid receptor agonist, and an ultra-loW dose of a nonselec selective kappal -opioid receptor agonist and nonselective tive opioid receptor antagonist, Wherein the doses are effec opioid receptor antagonist are administered as a single com tive in combination to promote analgesia in the subject and to position. reduce an adverse side effect of pain treatment With an opioid [0023] The separate compositions may be administered as receptor agonist administered singly in the subject. These separate compositions simultaneously or Within a short time methods include administering doses that are effective in frame. The separate compositions may be administered con combination to provide enhanced analgesia compared to secutively Within a short time frame in any order. “Combina analgesia from a moderate dose of either of said opioid recep tion” refers to more than one active compound or active tor agonists alone. pharmaceutical ingredient, including for example, a combi [0019] Treatment of chronic or persistent pain may result in nation of tWo opioid receptor agonists and nonselective long term administration of an opioid receptor agonist to a opioid receptor antagonist. subject, and adverse side effects are likely With long term [0024] The invention also provides for compositions com treatment. The invention also provides for methods of prising a moderate dose of a selective mu-opioid receptor enhancing analgesia With an opioid receptor agonist While agonist, a moderate dose of a selective kappa-opioid receptor reducing an adverse side effect of pain treatment With an agonist, e. g. kappa l -opioid receptor agonist, and an ultra-loW opioid receptor agonist, the method comprising administer dose of a nonselective opioid receptor antagonist, Wherein the ing to a subject suffering from pain, a moderate dose of a doses in combination are effective to reduce pain and to selective mu-opioid receptor agonist, a moderate dose of a reduce an adverse side effect of treatment With an opioid selective kappal-opioid receptor agonist, and an ultra-loW receptor agonist in a subject. The compounds of the invention dose of a nonselective opioid receptor antagonist, Wherein the are therapeutically effective to enhance the analgesic effect of doses are effective in combination to promote analgesia in the the opioid receptor agonists in the subject. The compositions subject and to reduce an adverse side effect of pain treatment of the invention are also therapeutically effective to reduce or With an opioid receptor agonist in the subject. These methods suppress hyperalgesic effects of long-term administration of include administering doses that are effective in combination an opioid receptor agonist in the subject. to provide enhanced analgesia compared to analgesia from a [0025] The compositions of the invention may be adminis moderate dose of either of said opioid receptor agonist. tered as an unit dose comprising a moderate dose of a selec [0020] The invention also provides for methods of promot tive mu-opioid receptor agonist, a moderate dose of a selec ing additive analgesia of pain treatment With opioid receptor tive kappa-opioid receptor agonist, e. g. kappal -opioid agonists in a subject While reducing an adverse side effect of receptor agonists, and an ultra-loW dose of a nonselective pain treatment With an opiate receptor agonist, the method opioid receptor antagonist, Wherein the doses in combination comprising administering to a subject suffering from pain a are effective to reduce pain and to reduce an adverse side moderate dose of a selective mu-opioid receptor agonist, a effect of treatment With an opioid receptor agonist in a sub moderate dose of a selective kappal -opioid receptor agonist, ject. and an ultra-loW dose of a nonselective opioid antagonist, [0026] In another embodiment, the invention provides for Wherein the doses are effective in combination to promote use of a moderate dose of a selective mu-opioid receptor analgesia in an additive manner and to reduce an adverse side agonist, a moderate dose of a selective kappal -opioid recep effect of pain treatment With an opioid receptor agonist in the tor agonist, and an ultra-loW dose of a nonselective opioid subject. receptor antagonist for the preparation of a medicament for [0021] The term “selective opioid receptor agonist,” reducing pain in a subject While reducing an adverse side including “selective mu-opioid receptor agoni sts” and “selec effect of treatment With an opioid receptor agonist in a patient tive kappa-opioid receptor agonists,” refers to compounds suffering from pain, Wherein the doses in combination are that primarily binds to and activate a speci?c opioid receptor effective to reduce pain and to reduce an adverse side effect of type treatment With an opioid receptor agonist in the subject. Use [0022] In any of the methods or uses of the invention, the of the medicament of the invention has the added bene?ts of doses of the three compounds (mu-opioid receptor agonist, enhancing the analgesic effects of an opioid receptor agonist, kappa-opioid receptor agonist s and opioid receptor antago reducing the hyperalgesic effect of treating pain With an nist) may be administered as separate compositions simulta opioid receptor agonist and promoting the additive analgesia neously or Within a short time frame before or after the other of pain treatment With an opioid receptor agonist. compositions. Alternatively, the doses of the three com [0027] The invention also provides for use of a moderate pounds may be administered in combination as a single com dose of a selective mu-opioid receptor agonist, a moderate position. In a further embodiment, the dose of the three com dose of a selective kappal-opioid receptor agonist, and an pounds are administered as tWo compositions in Which one ultra-loW dose of a nonselective opioid receptor antagonist compositions comprises tWo of the compounds and a second for the preparation of a medicament for treating a subject composition comprises one of the compounds. For example, suffering from pain With an opioid receptors agoni st, Wherein the mu-opioid receptor agonist and the kappa-opioid receptor the doses administered in combination are effective to US 2010/0227876 A1 Sep. 9, 2010

enhance the analgesic effect of the opioid receptor agonist in nist methadone (DOLOPHINE) at an exemplary analgesic the subject and the administered doses are effective to reduce moderate dose of 5-20 mg, administering the mu-opioid an adverse side effect of treatment With the opioid receptor receptor agonist fentyanyl (SUBLIMAZE) at an exemplary agonist in the subject. analgesic moderate dose of 0.07-025 1 mg, administering the [0028] The invention further provides for use of a moderate mu-opioid receptor agonist oxymorphone at an exemplary dose of a selective mu-opioid receptor agonist, a moderate analgesic moderate dose of 10-20 mg. dose of a selective kappal-opioid receptor agonist, and an [0033] The invention also provides for compositions, uses ultra-loW dose of a nonselective opioid receptor antagonist and methods of administering the kappal-opioid receptor for the preparation of a medicament for reducing the hyper agonist that is of the arylacetamide type such as spiradoline or algesic effect of treating a subject suffering from pain With an enadoline. For example, the invention provides for composi opioid receptor agonist, Wherein the doses administered in tions, uses and method of administering spiradoline at an combination are effective to reduce the hyperalgesic effect of exemplary moderate dose of 014-0042 mg, and composi the opioidreceptor agonist in the subject and the administered tions, uses and methods of administering the kappal-opioid doses in combination are effective to reduce an adverse side receptor agonist enadoline at an exemplary moderate does of effect of treatment With the opioid receptor agonist in the 0.08-0.12 mg. subject. [0034] The invention provides for compositions, uses and [0029] The invention also provides for use of a moderate methods of administering the nonselective antagonist is dose of a selective mu-opioid receptor agonist, a moderate naloxone or naltrexone. The invention provides for composi dose of a selective kappal-opioid receptor agonist, and an tions, uses and methods of administrating the nonselective ultra-loW dose of a nonselective opioid receptor antagonist antagonist nalxone at the exemplary dose of 25-125 ng and for the preparation of a medicament for promoting additive uses and methods of administering the nonselective antago analgesia of pain treatment in certain types of pain (cutaneous nist naltrexone at the exemplary ultra-loW dose of 50-250 ng. somatic) With opioid receptor agonists in a subject While [0035] In particular, the invention provides for composi reducing the adverse side effects of pain treatment With an tions, uses and methods of administering a combination of opioid receptor agonist in said subject, Wherein the doses tWo opioid receptor agonists in Which the selective mu-opioid administered in combination are effective to promote anal ge receptor agonist is fentanyl and the selective kappal-opioid sia in an additive manner in the subj ect and the administered receptor agonist is spiradoline, a combination in Which the doses in combination are effective to reduce an adverse side selective mu-opioid receptor is oxymorphone and the selec effect of pain treatment With an opioid receptor agonist. tive kappal-opioid receptor agonist is spiradoline, a combi [0030] The compositions and the doses of the opioid recep nation in Which the selective mu-opioid receptor agonist is tor agonists and opioid receptor antagonists may be admin fentanyl and the selective kappal agonist is enadoline, and a istered orally, intravenously, sublingually, transmucosally combination in Which the selective mu-opioid receptor ago (including buccally), intramuscularly, subcutaneously, nist is oxymorphone and the selective kappal agonist is ena intratracheally, intrathecally or transdermally. doline. [0031] In the methods, uses and compositions of the inven [0036] In addition, the invention provides for composi tion, the moderate doses of the selective mu-opioid receptor tions, uses and methods of administering a combination in agonist is a median quantity of agonist that effectively Which the selective mu-opioid receptor agonist is fentanyl, reduces, suppresses or alleviates clinical pain in a subject. the selective kappal agonist is spiradoline and the nonselec Furthermore, a moderate dose of the selective kappa-opioid tive opioid-receptor antagonist is naloxone, a combination in receptor agonist, such as the kappal -opioid receptor agonist Which the selective mu-opioid receptor agonist is oxymor of the arylacetamide type, is a median quantity of agonist phone, the selective kappal agonist is spiradoline and the Which in addition to effectively reducing suppressing or alle nonselective opioid-receptor antagonist is naloxone, a com viating clinical pain in a subject, provides additive or syner bination in Which the selective mu-opioid receptor agonist is gistic analgesia When combined With a mu-opioid receptor fentanyl, the selective kappal agonist is enadoline and the agonist and reduction of an adverse side effect induced by the nonselective opioid-receptor antagonist is naloxone, a com mu-opioid receptor agonist. In the methods, uses and com bination in Which the selective mu-opioid receptor agonist is positions of the invention, the ultra-loW dose of a nonselective oxymorphone, the selective kappal agonist is enadoline and antagonist of an opioid receptor is the smallest quantity of a the nonselective opioid-receptor antagonist is naloxone, a drug that is likely to produce an appreciable therapeutic combination in Which the selective mu-opioid receptor ago affect, and further suppresses the tolerance and emergence of nist is fentanyl, the selective kappal agonist is spiradoline and mu-opioid receptor agonist and kappa-opioid receptor ago the nonselective opioid-receptor antagonist is naltrexone, a nist induced hyperalgesia (OIH), Which results in an combination in Which the selective mu-opioid receptor ago enhanced analgesia from both agonists. nist is oxymorphone, the selective kappal agonist is spirado [0032] For example, the invention provides for composi line and the nonselective opioid-receptor antagonist is naltr tions, uses and methods of administering the mu-opioid exone, a combination in Which the selective mu-opioid receptor agonist hydrocodone (VICODIN) at an exemplary receptor agonist is fentanyl, the selective kappal agonist is analgesic moderate dose of 5-10 mg, administering the mu enadoline and the nonselective opioid-receptor antagonist is opioid receptor agonist of hydromorphone (DILAUDID) at naltrexone, and a combination in Which the selective mu an exemplary analgesic moderate dose of 0.5-1.3 mg, admin opioid receptor agonist is oxymorphone, the selective kappal istering the mu-opioid receptor agonist levorphanol (LEVO agonist is enadoline and the nonselective opioid-receptor DROMORON) at an exemplary analgesic moderate dose of antagonist is naltrexone. 0.5-2 mg, administering the mu-opioid receptor agonist oxy [0037] “Therapeutic effect” or “therapeutically effective” codone (PERCODON) at an exemplary analgesic moderate refers to an effect or effectiveness that is desirable and that is dose of 5-10 mg, administering the mu-opioid receptor ago an intended effect associated With the administration of an US 2010/0227876 A1 Sep. 9, 2010

opioid receptor agonist including When the opioid receptor [0044] An “analgesic dose of an opioid receptor agonist” agonist is administered in combination With an opioid antago refers to an amount of the opioid receptor agonist that causes nist according to the invention. Such therapeutic effects analgesia in a subject administered the opioid receptor ago include. e. g., analgesia, pain relief, decrease in pain intensity, nist alone, and includes standard doses of the agonist Which euphoria or feeling good, and calming so as to reduce heart are typically administered to cause analgesia (e.g., mg doses). rate, blood pressure and/or breathing rate. [0045] A “hypo-analgesic” amount is a less-than-analgesic [0038] The compositions, methods and uses of the inven amount, including an amount Which is not analgesic or is Weakly analgesic in a subject administered the opioid recep tion reduce, treat, lessen, ameliorate or suppress pain. The tor agonist alone, and further includes an “anti-analgesic” term “pain” refers to any type of pain, including e.g. long term persistent pain, chronic pain, acute pain, somatic pain, vis dosing schedule, Which results in an increase in pain. The ceral pain, and neuropathic pain. Visceral pain is of special optimum amounts, for example, of the opioid receptor ago nists and the opioid receptor antagonist administered in com interest since it is involved in severe and chronic cases of pain in Which opioid receptor agonist monotherapy has insu?i bination, Will of course depend upon the particular agonist ciencies. Moreover, mu-opioid and kappa-opioid receptor and antagonist used, the carrier chosen, the route of admin agonists in combination afford synergist and prolonged anal istration, and/ or the pharrnacokinetic properties of the subject gesia against this type of pain, and addition of a nonselective being treated, as Well as the desired gender-related effects opioid-receptor antagonist, further attenuates tolerance, according to the teachings of the present invention. depression, and emergence of OIH. [0046] The foregoing summary is not intended to de?ne every aspect of the invention, and additional aspects are [0039] The invention provides for compositions, uses and described in other sections, such as the Detailed Description. method of administering opioid receptor agonists and antago The entire document is intended to be related as a uni?ed nist to reduce pain in a subject, Wherein the subject may be disclosure, and it should be understood that all combinations any mammal including humans, non-human primates, horses of features described herein are contemplated, even if the and hoofed mammals, canines or felines. combination of features are not found together in the same [0040] The invention provides for compositions, uses and sentence, or paragraph, or section of this document. methods that reduce the adverse side effects resulting from [0047] In addition to the foregoing, the invention includes, treating a subject With a opioid receptor agonist. The inven as an additional aspect, all embodiments of the invention tion also provides for compositions, uses and methods for narroWer in scope in any Way than the variations speci?cally suppressing the emergence of adverse side effects or elimi mentioned above. With respect to aspects of the invention nating adverse side effects resulting from treating a subject described as a genus, all individual species are individually With an opioid receptor agonist. An effective reduction or considered separate aspects of the invention. With respect to suppressing of these side effects is determined by comparing aspects described as a range, all subranges and individual the effect resulting from treatment With a single opioid recep values are speci?cally contemplated. tor agonist With the effect resulting from administering a [0048] Although the applicant(s) invented the full scope of combination of a mu-opioid receptor agonist, a kappa-recep the claims appended hereto, the claims appended hereto are tor agonist and a opioid receptor antagonist. not intended to encompass Within their scope the prior art [0041] “Adverse side effect” refers to a medically undes Work of others. Therefore, in the event that statutory prior art ired consequences other than the one for Which a compound Within the scope of a claim is brought to the attention of the or treatment is intended, such as the negative effects produced applicants by a Patent Of?ce or other entity or individual, the by a drug, especially on a tissue or organ system other than the applicant(s) reserve the right to exercise amendment rights consequence sought to be bene?ted by its administration. The under applicable patent laWs to rede?ne the subject matter of invention provides for uses and methods that reduce the such a claim to speci?cally exclude such statutory prior art or adverse side effects of a mu-opioid receptor agonists. Some obvious variations of statutory prior art from the scope of exemplary adverse side effects of administration of an opioid such a claim. Variations of the invention de?ned by such receptor agonist include tolerance, dependence and hyperal amended claims also are intended as aspects of the invention. gesia, euphoria, anuria, pruritus, allodynia, and seiZures. In Additional features and variations of the invention Will be addition, the invention provides for uses and methods that apparent to those skilled in the art from the entirety of this reduce the opposing adverse side effects such as dysphoria, application, and all such features are intended as aspects of diuresis, antipruritus, and anti-allodynic induced by kappa the invention. opioid receptors. [0042] “Analgesia” refers to the attenuation, reduction or BRIEF DESCRIPTION OF DRAWINGS absence of sensibility to pain, including the provision of pain relief, the enhancement of pain relief, or the attenuation of [0049] FIG. 1 depicts the colorectal distension (CRD) pain intensity. model. The mean Maximum Percentage Analgesic Effect [0043] The term “analgesic dose” refers to a dose of a (M.P.E) (:S.E.M.) is plotted. Panel A depicts fentanyl, log composition or drug that effectively reduces, attenuates, doses, at 15 minutes post-inj ection (peak effect). ED5O (M.P. eases, suppresses or alleviates pain. An analgesic dose also E.:50%):0.009 mg/kg (range: 0.06-0.016 mg/kg); n:3-l6 refers to an amount that results in analgesic ef?cacy, for per dose. Panel B depicts spiradoline at 15 minutes post example, as measured by a subject With a pain relief score or injection (peak effect). ED5O:0.56 mg/kg (0.25-1.26 mg/kg); a pain intensity difference score, at a given time point, or over n:3-l2 per dose. Panel C depicts enadoline at 30 minutes time, or as compared to a baseline, and includes calculations post-injection (peak effect). ED5O:0.077 mg/kg (0.04-0.2 based on area under the curve such as those plotting Total Pain mg/kg); n:4-7 per dose. Panel D depicts oxymorphone at 30 Relief Score (TOTPAR) or the Sum of Pain Intensity Differ minutes post-injection (peak effect). ED5O:0.078 mg/kg ence (SPID). (0.02-0.126 mg/kg); n:5-9 per dose. Enadoline (kappa US 2010/0227876 A1 Sep. 9, 2010

opioid receptor agonist) and oxymorphone (mu-opioid recep opioid receptors predominate on A-delta ?bers (WerZ et al., J. tor agonist) served as typical agonist-class reference stan Pharmacol. Exp. Ther. 243: 258-63 (1987)). Visceral pain dards. systems distribute Widely, branching and diverging exten [0050] FIG. 2 depicts the antinociceptive responses in the sively (Bonica, The Management of Pain. 28-94 (1990)), CRD model. The mean M.P.E. (:S.E.M.) for actual combined explaining the phenomenon of referred pain. Visceral pain doses of opioid agonist pairs (?lled circles) vs. additive theo afferents make up only 2-15% of all afferent ?bers at various retical plots of single doses for each pair (?lled squares) is spinal cord levels (Ness et al., Pain. 41: 167-234 (1990)). The plotted at 15 minutes post-injections. FE displays fentanyl+ ratio of A-delta/ C ?bers in primary visceral afferents is l/s-1/1o enadoline plots, FS fentanyl+spiradoline plots, OE oxymor (promoting diffuse, Widespread activity), While the ratio in phone+enadoline plots, and OS oxymorphone+spiradoline dorsal root is 2/1 (favoring focal, discriminated reactions) plots; n:6-9 per dose. One dose, 0.6 in the OS panel, Was (Janig et al., Prog. Brain Res. 67: 87-114 (1986)). signi?cantly different from additive response, p<0.05. [0055] Studies, such as those described in MiaskoWski et al. [0051] FIG. 3 depicts the antinociceptive responses in the (Brain Res. 608: 87-94 (1993)) demonstrate that mu- and CRD model. The mean M.P.E. (:S.E.M.) of single opioid kappa-opioid agonist interactions produce antagonistic or agonists (fentanyl, spiradoline, enadoline) are compared With synergistic ANC, the latter accompanied by reduced side combined agonist pairs at tWo dose levels tested at 15 minutes effects. These studies used a mechanical nociceptive stimu (Panel A) and 30 minutes (Panel B) post-inj ection. * denotes lus, Which implies visceral-type pain mechanisms. Intracere additive interactions; ** denotes supra-additive (synergistic) broventricular (i.c.v.) injections delivered agonists to brain interactions, p<0.05; n:8-10 per dose. sites While intrathecal (i.t.) injections delivered them to spinal [0052] FIG. 4 depicts the antinociceptive responses for sites. Antagonism Was seen With i.c.v. injections of DPDPE combinations of a mu- and kappa-opioid receptor agonists (delta-opioid receptor agonist) combined With it. injections With pretreatment With an opioid receptor antagonist in the of DAMGO (mu-opioid receptor agonist). HoWever, most CRD model. The mean M.P.E. (:S.E.M.) for agonist-antago combinations produced enhanced ANC, the greatest synergy nist interactions are displayed for single and combined ago seen after combined i.c.v. injections of DAMGO and it. nists (fentanyl alone 0.12 mg, spiradoline alone 0.3 mg and a injections of U50,488H. combination of both agonists With pretreatment With an [0056] Results of these studies led to the proposed mecha opioid antagonist (beta-funeltrexamine ([3-FNA) or norbinal nism of multiple brain- spinal ascending-descending neuronal torphimine (nor-BNI) at 15 minutes (Panel A) and 30 minutes loops, With mu- and kappa-opioid receptors residing at junc (Panel B) post-injections. Panel A: * denotes a signi?cant tions of shared components. Multiple agonist actions at increase in M.P.E. for the combination of fentanyl and spira receptors in serial or parallel arrangements Were considered doline compared to either agonist alone (p<0.01). # denotes a to amplify the total ANC effect beyond the sum of the parts. signi?cant reduction in M.P.E. for fentanyl after pretreatment [0057] Consistent With the above theories, supra-spinal With an opioid receptor antagonist compared to saline pre dynorphin (endogenous kappa-opioid receptor agonist) treatment. @ denotes a signi?cant reduction in M.P.E. for the antagoniZed the ANC of morphine also injected supra-spi combination of agonists after pretreatment With an opioid nally, but supra-spinal dynorphin potentiated spinally-in receptor antagonist compared to saline pretreatment (p<0. duced morphine ANC (Ren et al., Peptides. 6: 1015-20 01). Panel B: ** denotes signi?cant increase in M.P.E. for the (1985)). Also, Stachura et al. (Pol. J Pharmacol. 45: 37-41 combination of fentanyl and spiradoline compared to either (1994)) reported potentiated ANC of SC morphine by spira agonist alone (p<0.05). doline injected intrathecally. ANC from morphine or U50, 488H in mice Was attenuated by increasing brain GABA DETAILED DESCRIPTION activity or reducing brain 5HT activity (N emmani et al., Neu [0053] The data provided herein demonstrates that dose ropharmacology. 44: 304-10 (2003)), indicating that complex response patterns of individual doses of the opioid receptor multiple interactions betWeen opioid receptor agonists and agonists, fentanyl and spiradoline, included full antinocicep other neurotransmitter systems also occur. tive effects (ANC) in the CRD visceral pain assay. Compari [0058] Neurochemical studies support these hypotheses. son of the theoretical combination effects of opioid receptor Both mu- and kappa-opioid receptors Were found on most agonists, measured as added sums of individual opioid recep nociceptive neurons throughout central and peripheral mam tor agonist responses, With actual combined effects of fenta malian nervous systems (AtWeh et al, Brain Res. 124: 53-67 nyl plus spiradoline, indicated primarily additive-response (1977); Allerton et al., Brain Res. 502: 149-57 (1989)). Inter patterns of ANC for these combinations. Higher-dose com actions may occur on peripheral A-delta ?bers and C ?bers, binations of fentanyl plus spiradoline produced supra-addi on dorsal root ganglion cells and synaptic endings, and on tive ANC at both 15 and 30 minutes post-injection (FIGS. 3 interneurons in dorsal horn or spinal projection cells. Also, and 4). Thus, combination of this mu-opioid agonist and this interactions occur in supra-spinal nuclei (especially PAG, kappa-opioid agonist at some dose levels enhanced the PVG, RVM, and raphe nuclei), as Well as in forebrain loci (see increase in the threshold for visceral pain in the CRD test Bie et al., J. Neurosci. 32: 7262-8 (2003), and He et al., J. model beyond an additive level. Pharmacol. Exp. Ther. 280: 1210-4 (1997)). [0054] Generally, mu- and kappa-opioid agonists induce [0059] In addition, kappa-opioid receptors Were found to responses on different receptors and types of pain, and With be involved in the same neuronal netWork in rat PAG that different e?icacies When they both affect the same type of controls morphine tolerance and dependence (Herra’eZ pain orpain test model (Ness et al., Pain. 41: 167-234 (1990)). Baranda et al. Brain Res. 137: 166-73, (2005)). This discovery Spinal ANC Was proposed to involve mu2-opioid receptors, relates to studies by He et al., J. Pharmacol. Exp. Ther. 280: While supra-spinal (brain) ANC involved mu1-opioid recep 1210-4 (1997), Jang et al., Arch. Pharm. Res. 29: 677-84 tors (Pasternak et al., Life Sci. 138: 1889-98 (1986). Mu (2006), Song et al., Life Sci. 51: 107-11 (1992), Tao et al., Eur opioid receptors predominate on C ?bers, Whereas kappa J Pharmacol. 1994 May 2;256(3):281-6.Links (1994), and US 2010/0227876 A1 Sep. 9, 2010

Yamamoto et al., Eur. J. Pharmacol. 156: 173-6 (1988), in an effect, and high naltrexone doses blocked CPP. Thus, it Which kappa-opioid agonists enhanced morphine ANC, Was concluded that ultra-loW doses of natrexone interfere reversing tolerance and/or dependence. Acute mu- and With the reWarding effects of analgesic doses of mu-opioid kappa-opioid agonists both inhibited glutamate input to receptor agonists, in addition to suppressing their aversive brain-stem ventral tegmental area neurons, but from different WithdraWal effects. sources (Margolis et al., J. Neurophysiol. 93: 3086-93 [0063] The present invention provides for compositions (2005)). But chronic opioid agonists activate glutamate and methods of reducing or treating pain With a combination mechanisms, promoting opioid-agonist tolerance and depen of a mu-opioid receptor agonist, a kappa-opioid receptor ago dence (Fundytus, CNS Drugs. 15: 29-85 (2001)). These types nist, and a nonselective opioid antagonist. These methods are of neuronal dichotomy Would alloW for potential synergistic directed to reducing and treating any type of pain, including or occlusive effects of combined agonists. Complex mu-/ for example long term persistent pain, chronic pain, subacute kappa-opioid interactions, With differential relationships of pain and acute pain. Chronic pain is continuous or recurrent. opioid receptors in visceral and cutaneous types of pain, Were Acute pain occurs in brief periods of time and is associated also elaborated by Schmauss et al. J. Pharmacol. Exp. Ther. With temporary disorders. The pain may be slight, moderate 228: 1-12 (1984) and Gebhart, Animal Pain. 81-93 (1992)). or severe. The types of pain that may be reduced or treated [0060] The majority opinion of pain therapists today still With the methods and compositions of the invention including adhere to the use of mu-opioid receptor agonist monotherapy nociceptive pain such as somatic pain and visceral pain, neu as the appropriate treatment for subacute or chronic moderate ropathic pain, muscle pain, colicky pain, and referred pain. to severe pain. These therapists remain convinced that kappa The invention provides for method of reducing or treating opioid receptor agonists have only a minor role in pain man pain caused by any source including postoperative pain and agement. Still, some authorities have recently promoted the pain associated With chronic diseases. use of combined opioids or opioid/non-opioid analgesics to [0064] The term “opioid” refers to “opioid-like com overcome the problems of mu-opioid receptor agonist mono pounds” or compounds or compositions including substitu therapy (Coop et al., Amer. .1. Pharm. Educ. 24: 198-205 ents of such compounds or compositions Which bind to spe (2002); McNaull et al., Eur JPharmacol. 560(2-3):132-41 ci?c opioid receptors and have agonist (binding/ activation) or (2007); Tucker et al., BMCAnesZhesiol. 5(1):2. (2005); Olm antagonist (inactivation) effects at these receptors, such as stead et al., Psychopharmacology (Berl). 181(3):576-81. opioid alkaloids, including the agonist morphine and its (2005)). HoWever, much of the opioid scienti?c community metabolite morphine-6-glucuronide and the antagonist naltr continues to conclude that all kappa-opioid receptor agonists exone and its metabolite and opioid peptides, including are antagonists of mu-opioid receptor agonist analgesia. For enkephalins, dynorphins and endorphins. The opioid can be example, McNally et al. (Neuroscience. 112(3):605-17 obtained from an opiate base or can be an opioid synthesiZed (2002)), cite in their revieW article the Work of Pan and col pharrnaceutically as an acceptable salt. The pharrnaceutically leagues in order to emphasiZe the incompatibility of mu acceptable salt may be an inorganic or an organic salt. Rep kappa-opioid combinations in pain therapy and to demon resentative salts include hydrobromide, hydrochloride, strate that the opioid scienti?c community had established the mucate, succinate, n-oxide, sulfate, malonate, acetate, phos fact that kappa-opioid receptor agonists interfered With the phate dibasic, phosphate monobasic, acetate trihydrate, analgesic effects of mu-opioid receptor agonists. bi(hepla?uorobutyrate), maleate, bi(methylcarbamate), [0061] Currently, drug development comprising analgesic bi(penta?uoropropionate), mesylate, bi(pyridine-3-carboxy combinations of mu-opioid receptor agonists and kappa1 late), bi(tri?uoroacetate), bitartrate, chlorhydrate, fumarate opioid receptor agonists to manage subacute or chronic and sulfate pentahydrate. The term “opiate” refers to drugs severe pain has been sloW. This disinterest is likely fostered derived from opium plants. by, at least partly, the complexities and di?iculties of analyZ [0065] An “opioid receptor agonist” or “opioid agonist” is ing combination-drug studies and their potential to increase an opioid compound or composition including any active research expense and delay or hamper approval of candidate metabolite of such compound or composition that binds to drugs for clinical use. In addition, there is an ingrained preju and/or activates opioid receptors, for example, binds to those dice in the ?eld against drug-combination therapy. Neverthe receptors on nociceptive neurons Which mediate pain such as less, some drug industry scientists are exploring opioid and binding and/or activating mu- or kappa-opioid receptors. nonopioid combinations to potentiate analgesia While reduc Such agonists have analgesic activity (With measurable onset, ing adverse side effects (see Baker et al., Pharmacol Biochem peak, duration and/or total effect) and can produce analgesia. Behav. 74(1):73-86 (2002)). Opioid agonists include: alfentanil, allylprodine, alphaprod [0062] Ultra-loW doses of opioid antagonists enhance ine, anileridine, apomorphine, apocodeine, benZylmorphine, opioid-induced analgesia and attenuate the adverse side beZitramide, buprenorphine, butorphanol, clonitaZene, effects of tolerance and WithdraWal. For example, small doses codeine, cyclaZocine, cyclorphen, cyprenorphine, desomor of naltrexone (antagonist) Were co-administered With mu phine, dextromoramide, deZocine, diampromide, dihydroco opioid receptor agonists, such as morphine or oxycodone, to deine, dihydromorphine, dimenoxadol, dimepheptanol, dim test for altered reWard effects or aversive effects of precipi ethylthiambutene, dioxyaphetyl butyrate, dipipanone, tated WithdraWal (Olmstead et al., Psychopharmacology eptaZocine, ethoheptaZine, ethylmethylthiambutene, ethyl (Berl). 81(3):576-81 (2005)). In these studies, pretreatment morphine, etonitaZene, fentanyl, heroin, hydrocodone, With naltrexone blocked the conditioned place preference hydroxymethylmorphinan, hydromorphone, hydroxypethi (CPP) of morphine and co-administration of naltrexone dine, isomethadone, ketobemidone, levallorphan, levorpha blocked the conditioned place aversion (CPA) to WithdraWal nol, levophenacylmorphan, lofentanil, meperidine, meptaZi from chronic oxycodone. It Was proposed that the effect of nol, metaZocine, methadone, methylmorphine, metopon, naltrexone on CPP training With oxycodone yielded a bi morphine, myrophine, nalbuphine, narceine, nicomorphine, phasic dose-pattern effect, the middle natrexone dose lacked norlevorphanol, norrnethadone, nalorphine, norrnorphine, US 2010/0227876 A1 Sep. 9, 2010

norpipanone, ohmefentanyl, opium, oxycodone, oxymor [0071] The term “ultra-loW dose” refers to a very small phone, papaveretum, pentazocine, phenadoxone, phenomor quantity relative to the Well-established/ conventional larger phan, phenazocine, phenoperidine, pholcodine, piminodine, quantities that are knoWn to produce an appreciable therapeu piritramide, propheptazine, promedol, profadol, properidine, tic effect. Generally, it can be expected that an ultra-loW dose propiram, propoxyphene, remifentanil, sufentanil, tramadol, Will produce a different effect than the Well-established tilidine, salts thereof, mixtures of any of the foregoing. higher dose. An ultra-loW dose of nonselective antagonist is a Opioid receptor agonists include naturally occurring opiates quantity that is effective for antagonizing mu- and kappa and pharmaceutically synthetic opioids. excitatory opioid receptors but that is beloW the threshold for [0066] “Bimodally-acting opioid agonists” are opioid ago antagonizing mu- and kappa-inhibitory opioid receptors. An nists that bind to and activate both inhibitory and excitatory exemplary threshold for antagonizing mu- and kappa-inhibi opioid receptors on nociceptive neurons Which mediate pain. tory opioid receptors is 5 mg of naltrexone. Activation of inhibitory receptors by said agonists causes analgesia. Activation of excitatory receptors by said agonists Adverse Side Effects results in anti-analgesia, hyperexcitability, hyperalgesia, as Well as development of physical dependence, tolerance and [0072] An “adverse side effect” of an opioid receptor ago other undesirable side effects. Bimodally-acting opioid ago nist is a medically undesirable signi?cant consequence of administration and this consequence is an effect other than the nists may be identi?ed by measuring the opioid’s effect on the effect for Which the opioid receptor agonist is intended. For action potential duration (APD) of dorsal root ganglion examples, an adverse side effect of an opioid receptor agonist (DRG) neurons in tissue cultures. In this regard, bimodally is a consequence other than amelioration or reduction or acting opioid agonists are compounds Which elicit prolonga suppression or attenuation of pain. Exemplary adverse side tion of the APD of DRG neurons at pM-nM concentrations effects of administration of opioid receptor agonists includ (i.e., excitatory effects), and shortening of the APD of DRG ing hyperalgesia, tolerance, nausea, vomiting, dizziness, neurons at [1M concentrations (i.e., inhibitory effects). somnolence/sedation, pruritus allodynia, reduced gas [0067] An “opioid antagonist” is an compound or compo trointestinal motility including constipation, peripheral sition including any active metabolite of such compound or vasodilatation including leading to orthostatic hypotension, composition that in a su?icient amount attenuates (e.g., headache, dry mouth, sWeating, asthenia, dependence, mood blocks, inhibits, or competes With) the action of an opioid changes (e.g., dysphoria, euphoria), mental clouding, leth agonist. An “effective antagonistic amount” is one Which argy, impairment of mental and physical performance, anxi attenuates the analgesic effectively activity of an opioid ago ety, fear, depression of the cough re?ex; miosis, clouded nist. An opioid antagonist binds to and blocks (e.g., inhibits) sensorium, skin rash, release of histamine, lightheadedness, opioid receptors, for example, binds to and blocks receptors ureteral spasm; spasm of vesical sphincter and urinary reten on nociceptive neurons Which mediate pain. Opioid antago tion; and tramadol: seizures; anaphylactoid reactions (less nists according to the present invention include: naltrexone, ened resistance to toxins), diarrhea; anuria, CNS stimulation naloxone nalmefene, naloxone methiodide, nalorphine, (“CNS stimulation” is a composite that can include nervous naloxonazine, nalide, nalmexone, nalbuphine, nalorphine ness, anxiety, agitation, tremor, spasticity, euphoria, emo dinicotinate, naltrindole (NTT), naltrindole isothiocyanate, tional lability and hallucinations); malaise, confusion, coor (NTII), naltriben (NTB), nor-binaltorphimine (nor-BN1), dination disturbance, euphoria, nervousness, sleep disorder; b-funaltrexamine ([3-FNA), BNTX, cyprodime, lCl-174,864, abdominal pain, anorexia, ?atulence, hypertonia, rash, visual LY117413, MR2266, or an opioid antagonist having the same disturbance, menopausal symptoms, urinary frequency, and pentacyclic nucleus as nalmefene, naltrexone, nalorphine, urinary retention. An adverse side effect may be a serious nalbuphine, thebaine, levallorphan, oxymorphone, butorpha adverse side effect such as respiratory depression or also nol, buprenorphine, levorphanol, meptazinol, pentazocine, apnea, respiratory arrest, circulatory depression, cardiac dezocine, or their pharmacologically effective esters or salts. arrest, hypotension or shock. An opioid antagonist With partial agonist activity is cholera toxin B. Mu-Opioid Receptor Agonists [0068] A “mixed opioid receptor agonist/antagonist is a compound that has an a?inity for tWo or more types of opioid [0073] A “mu-opioid receptor agonist” is an opioid recep receptors and blocks opioid effects on one receptor type While tor agonist that primarily binds to and/or interacts With mu producing opioid effects on a second receptor type. Mixed opioid receptors and from such interactions produces its opioid receptor agonist/antagonists include compounds that therapeutic effects (e.g., analgesic activity). Excluded from exhibit opioid receptor agonist action at one dose and have an the de?nition of mu-opioid receptor agonists are agents that antagonistic action at another dose. primarily bind to and activate kappa-opioid receptors, and [0069] The term “moderate analgesic dose” refers to a from such interactions produce their therapeutic effects (e. g., median quantity of a drug that effectively reduces, suppresses analgesic activity). or alleviates pain suffered by a subject. An exemplary mod [0074] Exemplary mu-opioid receptor agonist include erate dose is the ED5O as this dose exerts an effective thera hydrocodone (VICODIN), hydromorphone (DILAUDID), peutic action that is not near-maximal dose. A near maximal levorphanol (LEVO-DROMORON), oxycodone (PER effect is exerted at the ED-80 or ED-90 dose level. CODON), methadone (DOLOPHINE), fentyanyl (SUBLI [0070] The invention also provides for compositions, uses MAZE), sufentanil and morphine. Adverse side effects that and methods of administering the kappal-opioid receptor are particularly observed With monotreatment of a agonist spiradoline at an exemplary moderate dose of 0.14 mu-opioid-receptor agonist are euphoria, anuria, pruritus 0.42 mg, and administering the kappal -opioid receptor ago allodynia, and seizures. nist enadoline at an exemplary moderate does of 0.08-0.12 [0075] The invention provides for compositions compris mg. ing a moderate analgesic dose of a mu-opioid receptor agonist US 2010/0227876 A1 Sep. 9, 2010

and methods of administering a moderate analgesic dose of a chopharmacology. 155: 362-71 (2001). Arylacetamide mu-opioid-receptor agonist. Exemplary moderate analgesic kappa-opioid agonists (U50,488H, spiradoline, and enado dose ranges of hydrocodone (VICODIN) include 1-25 mg, line) are selective, Without direct mu-opioid effects (von Voi 1-10 mg, 2-12 mg, 5-10 mg, 5-15 mg, 10-20 mg, and 15-25 gtlander and LeWis, 1988). Antinociception of U50,488H mg. Exemplary moderate analgesic dose ranges of hydromor involves 5HT, being attenuated by 5HT antagonists, and phone (DILAUDID) include 0.25-5.0 mg, 0.25-1.5 mg, 0.5-2 GABA disinhibitory effects, but spiradoline antinociception mg, 05-10 mg, 0.6-1.2 mg, 075-125 mg, 0.8-1.3 mg, 0.9 is less dependent upon serotonin interactions. 1.5 mg, 1.0-2.0 mg, 1.0-2.5 mg, and 2.5-5.0 mg. Exemplary [0080] The invention provides for compositions compris moderate analgesic dose ranges include levorphanol (LEVO ing a moderate analgesic dose of a mu-opioid receptor agonist DROMORON) is 0.25-5.0 mg, 0.25-5.0 mg, 05-10 mg, 0.5 and methods of administering a moderate analgesic dose. 2.0 mg, 0.6 mg -1.2 mg, 0.75-1.25 mg, 0.8-1.3 mg, 0.9-1.5 Exemplary moderate analgesic dose ranges of spiradoline mg, 1.0-2.0 mg, 1.0-2.5 mg, and 2.5-5.0 mg. Exemplary includes 0.2-0.50 mg, 0.2-0.45 mg, 0.015-0.45 mg, 0.12-0.42 moderate analgesic dose ranges of oxycodone (PER mg, and 01-04 mg. Exemplary moderate analgesic dose CODON) include 1-25 mg, 1-20 mg, 2.5-25 mg, 2.5-10 mg, ranges of enadoline include 01-025 mg, 01-020 mg, 0.08 5-10 mg, 5-20 mg, 7.5-20 mg, 10-20 mg, and 15-25 mg. 0.12 mg, 0.08-0.15 mg, 0.05-0.12 mg, and 005-010 mg. Exemplary moderate analgesic dose ranges of methadone (DOLOPHINE) include 1-25 mg, 1-20 mg, 2.5-25 mg, 2.5-10 Nonselective Antagonists mg, 5-10 mg, 5-20 mg, 7.5-20 mg, 10-20 mg, and 15-25 mg. Exemplary moderate analgesic dose ranges of mu-opioid [0081] A “nonselective opioid antagonist” is an opioid receptor agonist fentyanyl (SUBLIMAZE) include 0.01-0.5 receptor antagonist that binds to/ or interacts With more than mg, 0.01-0.5 mg, 0.05-0.1 mg, 0.07-0.25 mg, 0.08-0.3 mg, one opioid receptor and primarily blocks or suppresses ago 0.09-0.4 mg and 0.1-0.5 mg. Exemplary moderate analgesic nist binding to or activation of at least tWo opioid receptors in dose ranges of mu-opioid receptor agonist oxymorphone the presence of an agoni st. The nonselective opioid antagonist (OPANA) include 1-25 mg, 1-20 mg, 2.5-25 mg, 2.5-10 mg, Will block the mu-opioid receptors, kappa-opioid receptors 5-10 mg, 5-20 mg, 7.5-20 mg, 10-20 mg, and 15-25 mg. and/or the delta-opioid receptors and thereby block or inhibit the opioid receptor’s therapeutic effects (e. g., analgesic activ Kappa-Opioid Receptor Agonists ity). Exemplary nonselective opioid receptor antagonists include naloxone (N LX), naltrexone (NTX), nalmefene, and [0076] A “kappa-opioid receptor agonist” is an opioid ago diprenorphine. nist that primarily binds to and/or activates kappa-opioid [0082] The invention provides for compositions compris receptors and from such interactions produces its therapeutic ing an ultra-loW dose of a nonselective opioid receptor effects (e.g., analgesic activity), including, for example, pen antagonist and methods of administering an ultra-lose dose of taZocine, nalbuphine and butorphanol. Excluded from the a nonselective opioid receptor antagonist. Exemplary ultra de?nition of kappa-opioid-receptor agonists are opioid recep loW dose ranges of naltrexone include 10 ng-500 ng, 50-250 tor agonists that primarily bind to or activates mu opioid ng, 60-200 ng, 75 ng-100 ng and 50-100 ng. Exemplary receptor agonists. Kappa-opioid receptor agonists induce ultra-loW doses of naloxone include 10-250 ng, 15-200 ng, antinociceptive effects. Mixed partial agonists act at mu- and 25-125 ng, 30 ng-100 ng and 50 ng-100 ng. kappa-opioid receptors, such as butorphenol and nalbuphine are also considered “kappa-opioid receptor agonists.” Animal Models [0077] Exemplary kappa-opioid receptor agonists include arylacetamide kappa agonists including spiradoline, enado [0083] The effectiveness of the claimed methods and anal line, U50,488, pentaZocine, dinorphin, bremoZocine, gesic compositions may be demonstrated in human clinical PD117302, U69593, MR2034, cyclaZocine, ethylketocycla trials and in animal models. Exemplary animal models Zonine, ketaZocine, butorphanol and nalbuphine. Adverse include those in Which the nociceptive stimulus is mechani side effects that are particularly observed With monotreat cal, electrical, thermal or chemical. ment of a kappa-opioid receptor agonist are dysphoria, diure [0084] One exemplary animal model is the colorectal dis sis, antipruritus, anticonvulsant and anti-allodynic. tension (CRD) assay Which serves Well as a visceral pain test [0078] Additional exemplary kappa-opioid receptor ago model in cats, dogs and rats (Briggs et al. Pharmacol Biochem nists include those described by: U.S. Pat. No. 4,923,863 Behav 60: 467-72, 1998). In this assay, pressuriZed air pulse hereby incorporated by reference in its entirety (e. g., morpho stimuli delivered to a balloon rectal catheter are used as a line derivatives); U.S. Pat. No. 6,1 10,947 hereby incorporated nociceptive stimulus in a restrained animal. The pressure by reference in its entirety (e. g., pyrrolidinyl hydroxamic acid pulse may be gradually increased and the nociceptive thresh compounds); U.S. Pat. No. 5,965,701 hereby incorporated by old is measured by abdominal contraction. reference in its entirety (e. g., kappa-opioid receptor peptides [0085] Nociceptive thresholds may be established in the With af?nity for the kappa-opioid receptor at least 1,000 times colorectal distension assay (CRD) in restrained subjects by greater than its af?nity for the mu-opioid receptor). air-pressure pulse-stimuli, in?ating the balloon-catheter. To [0079] Butorphanol, is a mixed partial agonist at mu- and insure a standard, reproducible, brief stimulus, a stimulus kappa-opioid receptors is considered one of the most potent pulse shaper may be used. The nociceptive stimulus is deliv agonists (effective at a human dose of 2 mg). Nalbuphine, is ered by opening the line from pressuriZed reservoir to the a less potent mixed partial opioid that is an agonist at kappa catheter (placed Within the subj ect’s rectum), then from cath opioid receptors and an antagonist at mu-opioid receptors eter to the open air over a maximal period of one second. (effective at a human dose of 5-10 mg). PentaZocine is also a Thus, at least 6 stimuli could be delivered over the span of one mixed partial agonist at mu- and kappa-opioid receptors minute. TWo stimuli are delivered Within 10 seconds, yielding (Hardman et al., Goodman and Gilman’s The Pharmacologi essentially identical signals to establish a valid response. The cal Basis of Therapeutics. 81-93 (1996); Walker et al., Psy air pressure to the balloon catheter placed in the rectum acti US 2010/0227876 A1 Sep. 9, 2010

vates noriceptives in the intestine Wall to induce a “guarding the norciceptive stimuli for a longer time period than if the response.” Another example of an animal model is the rat tail animal received a comparable dose of a single opioid receptor ?ick test as described by D’Amour et al., J Pharrnacol Exp agonist. Administration of a mu- and a kappa-opioid receptor Ther. 1941;72:74-9 (1941). In this test, the tail of a trained agonist in combination With an ultra-loW dose of a nonselec restrained rat is dipped into a cold solution, such as a solution tive opioid receptor antagonist Will cause the animal to have a of ethylene glycol and Water maintained at —100 C., or a hot loWer nociceptive threshold, such as the animal Will endure solution, such as Water bath at 520 C., or exposed to a radiant the nociceptive stimuli for a shorter time period compared to heat, as a nociceptive stimulus. The nociceptive threshold is those animals are administered the mu- and kappa-opioid determined by establishing latency from the time the tail is receptor agonists in the absence of a nonselective opioid dipped until the time the rat ?icked its tail from the cold receptor antagonist. solution as described in. [0091] Assays to measure adverse side effects caused by [0086] A mechanical stimulus, such as pressure, may be administration of opioid receptor agonists are Well knoWn in used as a nociceptive stimulus. Pressure in these tests may be the art. For example, the acetic acid Writhing test in rodents, as applied progressively or by gradual increases. The pressure is described by Litch?eld et al., J. Pharmacol. Exp. The}: 96: administered by a method that alloWs for measurable incre 99-113 (1949), may be used to measure the tWisting move ments. The nociceptive threshold may be measured by the ments or struggling behavior induced by opioid receptor ago length in time or the amount of pressure applied before the nist administration. For example, the mu- and kappa-opioid animal WithdraWs the paW or tail, the animal tries to release its receptor agonists and a nonselective opioid receptor antago trapped limb or in a vocalization, such as the Randall-Selitto nist is administered according to any of the methods of the assay as described by Anseloni et al., J, Neurosci. Methods invention. At various time points after this treatment, acetic 131 (1-2): 93-97, 2003). acid (eg 0.7% acetic acid solution) is injected intraperito [0087] In the paW WithdraWal test as described by Har neally (eg 30, 60, 120, 180 and 240 min after treatment). Ten greaves et al., Pain. January;32(1):77-88.(1988), a nocicep minutes after the injection of acetic acid, the Writhing tive stimulus, such as radiant heat, is applied to the paW that responses are counted for a set time period, Wherein an has been in?amed by an agent, such as subcutaneous injection increase in the number of tWisting movements indicates an of carrageenin or exposure to UV light. The nociceptive adverse side effect. threshold is determined by the length of time betWeen expo [0092] Any of the above-described assays, such as the cold sure to the nociceptive stimulus and WithdraWal of the paW Water tail ?ick assay and the CRD assay, may be modi?ed to from that stimulus. measure an adverse side effect such as tolerance, dependence [0088] Another exemplary animal model is the hot plate and pruitius (itching). In addition, scratching responses test, Which is carried out by introducing the animal to an induced by administration of opioid receptor agonists may be open-ended cylindrical space With a metallic ?oor that is monitored by videotaping the treated animals for a set time heated to a constant temperature by a thermode or boiling period as described in Ko & Naughton, (Anesthesiology Water as described by Woolfe et al., J. Pharrnacol. Exp. Ther. 92(3): 795-805, 2000), Wherein an increase in scratching 80:300-307. (1944). Reaction time to the heated plate is deter indicates an adverse side effect. mined by observing paW licking or jumping. Pharmaceutical Compositions [0089] Electrical stimuli may also be used in animal models of pain. For example, electrical stimulation of the tail may be [0093] The composition may be administered to the subject delivered as long lasting, gradually increasing, intensities by knoWn procedures including but not limited to oral, sub through a subcutaneous electrode inserted in the tail of a rat or lingual, transmucosal (including buccal), intramuscular, sub mouse as described by Carroll et al., Arch. Int. Pharmacodyn. cutaneous, intravenous, intratracheal, intrathecal or transder Ther. 125: 383-403 (1960). The nociceptive threshold may be mal modes of administration. When a combination of these measured by observing successive re?ex movement of the compounds are administered, they may be administered tail, vocaliZation at the time of stimulation and then vocaliZa together in the same composition, or may be administered in tion continuing beyond the period of stimulation. Altema separate compositions. If the opioid receptor agonists and the tively, an electronic stimulus may by delivered through elec opioid receptor antagonist are administered in separate com trically charged cage ?oors such as described by Blake et al. positions, they may be administered by similar or different Med Exp 9: 146-150 (1963). The nociceptive threshold is modes of administration, or may be administered simulta measured by behaviors such as animal tWitching, vocaliZa neously With one another, or shortly before or after the other. tion or attempting to escape the cage (the ?inch-jump test). [0094] The phrase “pharmaceutically acceptable” is used The electronic stimulus may be administered as single shocks herein to refer to those compounds, materials, compositions, or for very short time periods. As the stimulation increases, and/or dosage forms Which are, Within the scope of sound the folloWing responses are observed successively: tWitching, medical judgment, suitable for use in contact With the tissues escape behavior, vocaliZation and biting the electrodes. These of human beings and animals Without excessive toxicity, irri responses are hierarchically organiZed and the nociceptive tation, allergic response, or other problem or complication, threshold may be analyZed by the sensitivity to the test, as commensurate With a reasonable bene?t/risk ratio. described by NilsenActa Pharrnacol Toxicol (Copenh) 18: 10 [0095] The opioid agonists and the opioid antagonists may 22. (1 96 1 ). be formulated in compositions With a pharmaceutically [0090] For example, treatments that have an analgesic acceptable carrier. The carrier must be “acceptable” in the effect Will cause the animal to have a higher nociceptive sense of being compatible With the other ingredients of the threshold, such as the animal Will endure the nociceptive formulation and not deleterious to the recipient thereof. stimuli for a longer time. For the present invention, adminis Examples of suitable pharmaceutical carriers include lactose, tration of the combination of a mu- and a kappa-opioid recep sucrose, starch, talc, magnesium stearate, crystalline cellu tor agonist in the rat tail ?ick test Would cause a rat to endure lose, methyl cellulose, carboxymethyl cellulose, glycerin, US 2010/0227876 A1 Sep. 9, 2010

sodium alginate, gum arabic, powders, saline, Water, among ingredient) either each alone or in combination may conve others. The formulations may conveniently be presented in niently be presented to the subject for administration in unit unit dosage and may be prepared by methods Well-knoWn in dose form. the pharmaceutical art, by bringing the active compound into [0099] For oral or sublingual administration, including association With a carrier or diluent, as a suspension or solu transmucosal, the formulation may be presented as capsules, tion, or optionally With one or more accessory ingredients, tablets, caplets, pills, poWders, granules or a suspension, pre e.g., buffers, ?avoring agents, surface active agents, or the pared by conventional means With pharmaceutically accept like. The choice of carrier Will depend upon the route of able excipients, e.g., With conventional additives or ?llers administration. such as lactose, mannitol, corn starch or potato starch; With [0096] The opioid agonists or opioid antagonists may be binders or binding agents such as crystalline cellulose, cellu provided in the form of free bases or pharmaceutically accept lose derivatives, acacia, com starch (including pregelati able acid addition salts. As used herein, “pharmaceutically niZed) or gelatins; With disintegrators or disintegrants such as acceptable salts” refer to forms of the disclosed compounds corn starch, potato starch or sodium carboxymethyl-cellu Wherein the therapeutic compound is modi?ed by making lose; or With lubricants or Wetting agents such as talc or acid or base salts thereof. The “pharmaceutically acceptable magnesium stearate. Tablets may be coated, including by salt” embraces an inorganic or an organic salt. methods Well knoWn in the art. The formulation may be [0097] Examples of pharmaceutically acceptable salts presented as an immediate-release or as a sloW-release, sus include, but are not limited to, mineral or organic acid salts of tained-release or controlled-release form. The formulation the opioid antagonist or opioid agonist. The pharmaceutically may also be presented as a solid drug matrix. Oral dose forms acceptable salts include the conventional non-toxic salts for human administration include: codeine, dihydrocodeine made, for example, from non-toxic inorganic or organic (e.g., SYNALGOS-DC from Wyeth-Ayerst Pharmaceuti acids. For example, such conventional non-toxic salts include cals), fentanyl (e.g., ACTIQ from Abbott Laboratories), those derived from inorganic acids such as hydrochloric, hydrocodone (e.g., VICODIN and VICOPROFEN from hydrobromic, sulfuric, sulfonic, sulfamic, phosphoric, nitric, Knoll Laboratories; NORCO from Watson Laboratories; and others knoWn to those skilled in the art; and the salts HYCODAN from Endo Pharmaceuticals; NORCET from prepared from organic acids such as amino acids, acetic, Abara; ANEXSIA, HYDROCET, and LORCET-HD from propionic, succinic, glycolic, stearic, lactic, malic, malonic, Mallinckrodt; LORTABS from UCB Pharna; HY-PHEN tartaric, citric, ascorbic, pamoic, maleic, hydroxymaleic, phe from Ascher; CO-GESIC from SchWarZ Pharma; ALLAY nylacetic, glutamic, benZoic, salicylic, sulfanilic, 2-acetoxy from Zenith Goldline), hydromorphone (e.g., DILAUDID benZoic, fumaric, toluenesulfonic, methanesulfonic, ethane from Knoll), levorphanol (e.g., LEVO-DROMORAN from disulfonic, oxalic, isethionic, glucuronic, and other acids. ICN Pharmaceuticals), meperidine (e.g., DEMEROL from Other pharmaceutically acceptable salts and variants include Sano? Pharmaceuticals), methadone (e.g., METHADOSE mucates, phosphate(dibasic), phosphate(monobasic), acetate from Mallinckrodt; and DOLOPHINE HCl from Roxane trihydrate, bi(hepta?ourobutyrate), bi(methylcarbamate), Laboratories), morphine (e.g., KADIAN from Faulding bi(penta?ouropropionate), mesylate, bi(pyridine-3-carboxy Laboratories, MS CONTIN from Purdue Frederick; late), bi(tri?ouroacetate), bitartrate, chlorhydrate, and sulfate ORAMORPH SR from Roxane), oxycodone (e.g., PERCO pentahydrate. An oxide, though not usually referred to by CET and PERCODAN from Endo; OXYCET from Mallinck chemists as a salt, is also a “pharmaceutically acceptable salt” rodt; OXYCONTIN from Purdue Frederick; TYLOX from for the present purpose. For acidic compounds, the salt may Ortho-McNeil Pharmaceutical; ROXICODONE, ROXILOX include an amine-based (primary, secondary, tertiary or qua and ROXICET from Roxane), pentaZocine (e.g., TALACEN ternary amine) counter ion, an alkali metal cation, or a metal and TALWIN from Sano? Pharmaceuticals), propoxyphene cation. Lists of suitable salts are found in texts such as Rem (e.g., DARVOCET-N and DARVON from Eli Lilly & Co.; ington’s Pharmaceutical Sciences, 18”’ Ed. (Alfonso R. DOLENE from Lederle; WYGESIC from Wyeth-Ayerst), Gennaro, ed.; Mack Publishing Company, Easton, Pa., 1990); and tramadol (e. g., ULTRAM from Ortho-McNeil Pharma Remington: the Science and Practice of Pharmacy 19”’ Ed. ceutical). (Lippincott, Williams & Wilkins, 1995); Handbook of Phar [0100] Liquid preparations for oral administration may maceutical Excipients, 3.sup.rd Ed. (Arthur H. Kibbe, ed.; take the form of, for example, solutions, syrups or suspen Amer. Pharmaceutical Assoc., 1999); the Pharmaceutical sions, or they may be presented as a dry product for consti Codex: Principles and Practice of Pharmaceutics 12”’ Ed. tution With Water or other suitable vehicle before use. Such (Walter Lund ed.; Pharmaceutical Press, London, 1994); The liquid preparations may be prepared by conventional means United States Pharmacopiea: The National Formulary With pharmaceutically acceptable additives such as suspend (United States Pharmacopeial Convention); and Goodman ing agents (e.g., sorbitol syrup, methyl cellulose or hydroge and Gilman’s: the Pharmacological Basis of Therapeutics nated edible fats); emulsifying agents (e.g., lecithin or aca (Louis S. Goodman and Lee E. Limbird, eds.; McGraW Hill, cia); non-aqueous vehicles (e.g., methyl or propyl-p 1992), the disclosures of Which are hereby incorporated by hydroxybenZoates or sorbic acid). Liquid dose forms for reference. human administration include: hydrocodone (e. g., HYDRO [0098] “Unit dose form” or “unit dosage form” refers to PHANE) from Halsey), hydromorphone (e.g., DILAUDID physically discreet units suitable as unitary doses for human from Knoll), meperidine (e.g., DEMEROL from Sano?), subjects or veterinary subjects, each unit containing a prede methadone (e.g., DOLOPHINE from Roxane), oxycodone termined quantity of active material calculated to produce the (e.g., HYCOMINE from Knoll; ROXILOX from Roxane), desired therapeutic effect (e. g., analgesia), in association With and propoxyphene (e.g., DARVON-N from Eli Lilly). a suitable pharmaceutical carrier. Thus, the active ingredients [0101] For parenteral administration, including intrave according to the invention (e. g., opioid receptor agonist, nous, intramuscular, or subcutaneous administration, the opioid receptor antagonist, or other active pharmaceutical compounds may be combined With a sterile aqueous solution US 2010/0227876 A1 Sep. 9, 2010

Which is preferably isotonic With the blood of the recipient. testing paradigms. These play periods Were interspersed Such formulations may be prepared by dissolving solid active betWeen testing periods for one to tWo hours per interval. ingredient in Water containing physiologically compatible substances such as sodium chloride, glycine, or the like, and/ Drugs or having a buffered pH compatible With physiological con [0105] The opiate receptor agonists used in the studies are ditions to produce an aqueous solution, and/ or rendering said set out in Table l. Agonists Were dissolved in saline solution. solution sterile. The formulations may be present in unit dose Drugs and saline Were injected subcutaneously (SC) via sepa forms or multi-dose forms, including in containers such as rate syringes at different sites under the skin of the back of the sealed ampoules or vials. Parenteral dose forms for human neck. administration include: alfentanil (e.g., ALFENTA from Akom), buprenorphine (e.g., BUPRENEX from Reckitt & TABLE 1 Colman Pharmaceuticals), butorphanol (e.g., STADOL from Drug Type of Agonist Source Apothecon), deZocine (e.g., DALGAN from AstraZeneca), fentanyl, hydromorphone (e.g., DILAUDID-HP from Knoll), Fentanyl mu-opioid receptor Elkins-Sims, Inc., Cherry Hill, citrate (F) selective agonist NJ, USA levallorphan (e. g., LORFAN from Roche), levorphanol (e.g., Spiradoline kappa-opioid receptor Supplied by Dr. P. L. von LEVO-DROMORAN from ICN), meperidine (e.g., selective agonist Voigtlander, Upjohn, DEMEROL from Sano?), methadone (e.g., DOLOPHINE Kalamazoo, MI, USA HCI from Roxane), morphine (e.g., ASTRAMORPH from Enadoline kappa-opioid receptor Supplied by Dr. David DoWns, selective agonist Parke-Davis Pharmaceutical AstraZeneca; DURAMORPH and INTMORPH from Elkins Research, Ann Arbor, MI Sinn), oxymorphone (e.g., NUMORPHAN from Endo), nal Oxymorphone mu-opioid receptor Mallinckrodt, Mundelein, IL burphine (e.g., NUBAIN from Endo Pharmaceutical), and selective agonist pentaZocine (TALWIN from Abbott). [0102] For transdermal administration, the compounds [0106] The opioid antagonists beta-funaltrexamine may be combined With skin penetration enhancers such as ([3-FNA) and nor-binaltorphimine (n-BNI) Were dissolved in propylene glycol, polyethylene glycol, isopropanol, ethanol, sterile Water and Were supplied by the National Institute on oleic acid, N-methylpyrrolidone, or the like, Which increase Drug Abuse, Bethesda, Md., USA. Drugs and saline Were the permeability of the skin to the compounds, and permit the injected in separate injections (not separate syringes) by the compounds to penetrate through the skin and into the blood subcutaneous route (SC). stream. The compound/enhancer compositions also may be combined additionally With a polymeric substance such as Nociceptive Stimulus Equipment and Parameters ethylcellulose, hydroxypropyl cellulose, ethylene/vinylac [0107] The CRD assay Was used to establish the nocicep etate, polyvinyl pyrrolidone, or the like, to provide the com tive thresholds (pain thresholds). In the CRD assay, air-pres position in gel form, Which canbe dissolved in solvent such as sure pulse-stimuli Were administered to restrained subjects methylene chloride, evaporated to the desired viscosity, and through in?ation of a balloon-catheter. To insure a standard then applied to backing material to provide a patch. Trans reproducible brief stimulus, a stimulus-pulse shaper Was dermal dose forms for human administration include fentanyl devised, Which consisted of a 4-liter glass-jar reservoir ?tted (e.g., DURAGESIC from Janssen). With tubing and three-Way stop-cocks yoked to the jar, the [0103] Additional dose forms available as suppositories for catheter, a sphygmomanometer, a bicycle pump, and a port to human administration include oxymorphone (e. g., NUMOR room air. The reservoir Was charged With a pressure-head PHAN) from Endo). betWeen 40 and 180 mm Hg to accommodate sub-threshold, threshold, and antinociceptive responses. The nociceptive EXAMPLES stimulus Was delivered by opening the line from the reservoir to the catheter (placed Within the subj ect’s rectum), then from Example 1 catheter to the open air over a maximal period of one second. Thus, at least 6 stimuli could be delivered over the span of one Colorectal Distension Assay minute. TWo stimuli Were delivered Within 10 seconds, yield ing essentially identical signals (or lack of), to establish a [0104] Sensitivity for pain Was analyZed using the colorec valid response. tal distension assay (CRD) as described by SaWyer et al., J [0108] Initial loWer sub-threshold pressure-pulses, fre Amer Hosp Assoc 1987; 23: 438-46 (1987). For the studies quently and randomly presented, extinguished incidental described herein, male Sprague-DaWley rats (about 220 rats) conditioning. When a threshold pulse or greater Was deliv Weighing 300 to 500 grams Were approved for use by the ered, the rat responded With an abdominal contraction All-University Committee onAnimal Use and Care of Michi (“guarding re?ex”). This nociceptive response Was measured gan State University in accordance With NIH standards. All via a Water-?lled doughnut, Disposa-Cuff (Critikon, Tampa, animals Were trained over a tWo-month period to adjust to Fla.), ?tted around the subject’s abdomen. Tubing from the insertion of a lubricated (KY Jelly, Skillman, N.J., USA) Disposa-Cuff to a pressure transducer relayed the signal to a colonic balloon-catheter (Pointe Medical, CroWn Point, Ind., polygraph recorder (Grass Instruments, Quincy, Mass.). The USA) via the rectum. Subjects Were preconditioned to lie maximal amplitude of pressure pulses Was restricted to avoid quietly in a toWel Wrapped snugly around them and tolerate any potential tissue damage. the catheter in place over extended periods. The animals Were offered “treats” and subsequent “play and socialiZing time” Dose-Response Determinations of Agonists on a large table top With cage mates among toWels, boxes and [0109] After a nociceptive threshold Was determined, the tubes (“toys”) in order to reduce the stress induced by the balloon-catheter Was removed and the rat Was released from US 2010/0227876 Al Sep. 9, 2010

the towel to be injected subcutaneously With a coded (re CRD assay Were determined. Individual mean log-dose-re searcher blinded) drug or placebo, using mild hand restraint. sponse patterns (:SEM) in the CRD assay for fentanyl, spi The subject Was then toWel-restrained again for nociceptive radoline, enadoline, and oxymorphone formed linear slopes testing at 15-minute intervals for 30 minutes or as long as ranging from just signi?cant to full antinociception (ANC) three hours post-injection. Subjects that had been tested only With little deviation (FIG. 1). Fentanyl duration Was 50 min With single drugs Were used again (no more than 3 times) in utes With an ED5O of 0.01 mg/kg (range: 0.06-0.016) and a later tests, but only after a minimum of a Week and after three peak effect at 15 minutes post injection (FIG. 1A). Spirado daily typical threshold (placebo) responses. The opioid ago line duration Was 2 hours With an ED5O of 0.56 mg/kg (range: nists Were ?rst tested alone for log-dose patterns of antinoci 0.25-1.26) and a peak effect at 15 minutes post injection (FIG. ception for fentanyl, spiradoline, enadoline, and oxymor 1B). Oxymorphone and enadoline served as typical-class ref phone. The details and results of this experiment are provided erence comparisons. Enadoline (kappa-opioid receptor ago in Example 2 beloW. nist)had a ED5O:0.077 (004-02) and a peak effect at 30 [0110] The theoretical additive effect of single doses of minutes post-injection (FIG. 1C). Oxymorphone (mu-opioid agonist pairs Were compared With the actual effects of com receptor agonist) had an ED5O:0.078 (0.02-0.126) and a peak bined agonist pairs using the folloWing protocol. The single effect at 30 minutes post-injection (FIG. 1D). dose levels of agonists that produced antinociceptive effects that ranged from approximately 20-50% maximal percentage [0114] Subsequently, the actual responses of the drug com effects (see beloW) Were combined and tested for the actual binations Were compared to their theoretical sums set out in combined-agonist scores. Statistical comparisons of the theo FIG. 1. At 15 minutes post-injection, the results indicated retical and actual scores, the method for Which is described mostly additive ANC interactions, With one exception (FIG. beloW, established the additive, sub-additive or supra-addi 2). The exception Was one point of actual combined-dose tive differences of the actual combined-agonist interactions values of oxymorphone plus spiradoline (FIG. 2D), Which relative to their single dose effects. Details and results of this yielded a supra-additive (synergistic) effect. Otherwise the study are provided in Example 2 beloW. actual combined effects of the 4 agonist pairs (singly scoring [0111] TWo additional tests of combined fentanyl-spirado 20-50% Maximum Percentage Analgesic Effect (M.P.E.)) line and fentanyl-enadoline Were conducted to determine formed fairly linear slopes not signi?cantly different from the theoretical slopes of added single doses at 15 minutes post antinociceptive interactions at 15 and 30 minutes post-inj ec tion for a high and loW dose level. This study is described in injection. The data in FIG. 2 is displayed as log dose of each detail in Example 3. drug, combined to test additive and potential synergistic action. The log ratios alloW for comparisons betWeen the Selective Agonist-Antagonist Determinations theoretical and actual combined dose values. [0112] Prior to testing, one Set of three groups of rats Were [0115] An M.P.E. is the maximum percentage analgesic pretreated With saline for 24 or 48 hours before testing. effect of a designated dose. For example, fentanyl at a dose of Another Set of three groups of rats Were pretreated With 8 0.02 mg/kg Would produce near-maximal analgesia (M.P.E. mg/kg [3-FNA (mu-selective antagonist, Ward et al., J. Phar :90%+) in the CWTF. An ED-50 dose Would be about 0.009 macol. Exp. The}: 220: 494-8 (1982) for 24 hrs before testing. mg/kg (M.P.E.:50%), and an ED-10 Would likely be 0.003 A third Set of three rats Were pretreated With 10 mg/kg n-BNI mg/kg (M.P.E.:10%). (kappa-selective antagonist, Jones et al., Eur: J. Pharmacol. [0116] The results of loW- and high-dose combinations of 215: 345-8 (1998) for 48 hours before testing. Subsequently, fentanyl plus spiradoline and fentanyl plus enadoline, tested all 3 Sets received 0.012 mg/kg fentanyl, 0.3 mg/kg spirado for ANC at 15 minutes and 30 minutes post-injection, are line, or the combination, and Were tested for nociceptive shoWn in FIG. 3. threshold 15 and 30 minutes later. Table 2 lists n values for [0117] Full ANC levels for either class of opioid agonist groups and depicts a grid of treatments these subjects Were observed in the cold-Water tail-?ick assay (CWTF) as received. described in Briggs et al., Pharmacol. Biochem. Behav. 60: 467-72 (1998). HoWever, the dose-effect pattern of ANC for TABLE 2 the combination in the CWTF as say differed from that in the CRD assay described herein. In CWTF, loW-dose combina Number of Subjects, Pretreatment and Treatment Conditions for Grid Testing Agonist-Antagonist Interactions in CRD tions produced additive effects, While high-dose combina tions produced sub-additive or antagonistic interactions. In Set I: Saline Set II: [5-FNA<“> Set In; nor-BNI(b) CRD, loW doses in combination induced additive effects and pretreatment pretreatment pretreatment the combination of high doses resulted in supra-additiveANC F sp c F Sp 0 F Sp 0 patterns. [0118] In FIG. 3 (left-hand panel A), ANC of the loW-dose 8 rats 8 rats 10 rats 4 rats 4 rats 6 rats 4 rats 4 rats 6 rats fentanyl Was greater than that of the higher-dose fentanyl (“)beta-Funaltrexone, 8 mg/kg SC, 24 hrs before test response (right-handpanel A). This anomaly may relate to the (b)nor-Binaltorphimine, 10 mg/kg SC, 48 hrs before test repeated testing of the subjects (maximum of 3 treatments) @F = fentanyl 0.012 mg/kg With single doses of opioid receptor agonists, even though (@Sp = spiradoline 0.3 mg/kg (E)C = combined agonists these treatments Were spaced a Week apart and at least 3 days of placebo tests Were carried out betWeen treatments. Pearl et al., Neurosci. Len. 213: 5-8 (1996) reported interactions of Example 2 U50,488H or spiradoline With morphine, reducing morphine Antinociceptive Responses of Combinations of enhancement of locomotor activity When morphine Was Opioid Agonist injected 19 hours after administration of either kappa-opioid [0113] To analyZe the antinociception (ANC) for several receptor agonist. The kappa-opioid receptor antagonism Was opioid agonists, the theoretical sums of these agonists in the further strengthened by 2 days of morphine pretreatment. US 2010/0227876 A1 Sep. 9, 2010 14

Thus, mu- and kappa-receptor opioid agonistic in?uences on [0121] As shoWn in FIG. 4B, at thirty-minutes post-injec neuroplasticity appear to far outlast (45 hours or more) the tion, the analgesic effect of the combination of fentanyl and usual ANC duration of single-dose effects. spiradoline after saline pretreatment Was signi?cantly reduced compared to the analgesic effect induced by the Example 3 combination 15 minutes post-injection shoWn in Panel A (** Antinociceptive Responses for Combined Agonists p<0.0l). HoWever, the analgesic effect induced by the com and Antagonists bination 30 minutes post-injection Was signi?cantly greater then any of analgesic effects of the agonist alone or in com [0119] The high-dose combination of fentanyl plus spira bination after pretreatment With opioid receptor antagonists doline resulted in supra-additive interactions at both time (* p<0.0l). periods tested (15 and 30 minutes post injection, FIG. 3 [0122] After saline pretreatment, both fentanyl and spira left-hand panel A). Tests of the other dose combinations doline individually produced an approximate ED2O ANC formed additive response patterns. The single loW dose of response at the 15-minute test period (mean M.P.E. for fen fentanyl in panel A scored a higher M.P.E. (45, 15 minutes) tanyl:21% and for spiradoline:22%). The drug combination than the single high dose of fentanyl (18, 15 minutes). Fen after saline pretreatment induced prominent synergistic ANC tanyl “freezing” behavior (catalepsy) Was not observed in this (mean M.P.E. for C:68%). At the 30-minute test, the com study. FIG. 4 presents the single antinociceptive-dose effects bined agonists continued to manifest a supra-additive effect of fentanyl (0.012 mg/kg), spiradoline (0.3 mg/kg), and the in the saline-pretreatment group (mean M.P.E.:38%), com combined-dose effects of opioid receptor agonists after saline pared to the mean single-dose fentanyl score of 14% and the pretreatment, beta-funeltrexamine ([3-FNA) pretreatment, or mean single-dose spiradoline score of 3%. nor-binaltorphimine (n-BNl) pretreatment in three “Sets” of [0123] Surprisingly, the fentanyl M.P.E. score Was not rats (9 groups in all). reduced after [3-FNA pretreatment compared to that of the [0120] As shoWn in FIG. 4A, the combination of fentanyl saline-pretreatment group (30% vs. 21%) at the 15-minute and spiradoline after saline pretreatment induced a signi? test period. The spiradoline M.P.E. Was signi?cantly cantly greater analgesic effect, as measured by the Maximal decreased (4% vs. 22%) after [3-FNA in this period. The Percentage Analgesic Effect (M.P.E), than fentanyl alone (*, combined agonists after [3-FNA resulted in a score signi? p<0.0l), or spiradoline alone (*, p<0.0l) 15 minutes after cantly reduced (33%) compared to the combined agonists’ injection. Pretreatment With an opioid receptor antagonist score in the saline-pretreatment group (68%). ([3-FNA or nor-BNl) did not affect the analgesic effect of [0124] The n-BNI pretreatment failed to signi?cantly alter fentanyl alone compared to fentanyl pretreated With saline. the individual agonist scores at either the 15- or 30-minute The analgesic effect of spiradoline Was signi?cantly reduced test periods compared to those of saline controls. HoWever, With [3-BFA pretreatment When compared to spiradoline pre the score of the combined drugs after n-BNI Was much loWer treated With saline (#, p<0.01). The analgesic effect of the compared to those of saline-pretreatment rats (18% vs. 68% combination of fentanyl and spiradoline, after pretreatment at the 15-minute test, and 13% vs. 38% at the 30-minute test). With [3-FNA or nor-BNI, Was signi?cantly greater than the [0125] To emphasiZe the difference of the paradoxical analgesic effect induced by fentanyl alone or spiradoline effects in FIG. 4 compared to the agonist-antagonist interac alone With saline pretreatment (* p<0.05). HoWever, the anal tions found in the CWTF assay (Briggs et al., Pharmacol. gesic effect of the combination after pretreatment With an Biochem. Behav. 60: 467-72 (1998), the results from the opioid receptor antagonist Was signi?cantly reduced com CWTF study are repeated in Table 3. Using the CWTF assay, pared to the effect of the combination With saline pretreat the mean M.P.E. of fentanyl Was 86% and that of spiradoline ment (@, p<0.0l). These data demonstrate that the combina Was 77% after saline pretreatment. After [3-FNA pretreatment tion of mu- and kappa-opioid receptor agonists in the the fentanyl score Was signi?cantly reduced to 21%. The presence of an ultra-loW dose of an opioid receptor antagonist spiradoline score Was a non-signi?cant decrease to 67%. induces a greater analgesic effect than administration of an After n-BNI pretreatment, the fentanyl score Was 73% and the opioid receptor agonist alone. spiradoline score Was signi?cantly reduced to 13%.

TABLE 3

Antinociception of Fentanyl (F) and Spiradoline (Sp) Using the Cold-Water Tail-Flick Assay in Saline-, [5-FNA-, or n-BNI-Pretreated Rats. (From Briggs et al., Pharmacol. Biochem. Behav. 60: 467-72 (1998)

Saline (a) [?-FNA (a) n-BNI (b)

S F Sp S F Sp S F Sp

M.P.E. 1.0 86 +/— 6 77 +/— 8 1.0 21 +/— 10 67 +/— 12 1.0 73 +/— 9 13 +/— 5

(a) Saline or beta-funaltrexone ([i-FNA), 8 mg/kg, pretreatment Was injected SC 24 hrs before testing. (b) nor-Binaltorphimine (n-BNI), 10 mg/kg, Was injected SC 48 hrs before testing. (0) Maximal percent effect, antinociceptive values are means +/— S.E.M., n = 6 for each group. (d) Values of F and Sp differ signi?cantly, p < 0.01, from F and Sp a?er saline pretreatment, respectively. S (saline), F (fentanyl, 0.018 mg/kg), or Sp (spiradoline, 1.0 mg/kg), Was injected SC 15 min prior to antinociceptive testing. US 2010/0227876 A1 Sep. 9, 2010

[0126] Regarding agonist-antagonist interactions (fentanyl need for greater knoWledge and research in the areas of vis plus spiradoline, [3-FNA plus n-BNI), prior results in the ceral pain and for candidate opioid and non-opioid therapies. CWTF assay (discussed above) Were straightforward. [3-FNA This revieW emphasized the discovery of the dorsal column (mu-selective antagonist) markedly decreased the ANC of pain pathWay, further integrating spinal and supraspinal noci fentanyl Without a signi?cant change in spiradoline ANC. ceptive and ANC mechanisms, thus identifying neW sites at After n-BNI (kappa-speci?c antagonist), a reduced ANC of Which drugs may interact to modulate visceral pain mecha spiradoline (selective kappa-opioid receptor agonist) nisms. Extensive research on this topic Would likely aid in the occurred, While no signi?cant change in the ANC of fentanyl development of more effective therapies. Was observed. HoWever, agonist-antagonist interactions in CRD (FIG. 4) resulted inparadoxical reactions. After [3-FNA, fentanyl ANC-CRD tended to increase (non-signi?cantly) Example 4 While spiradoline ANC Was attenuated, relating to individual agonist effects in saline-pretreatment subjects. After n-BNI, Fentanyl and Spiradoline Interactions for Place Con neither fentanyl nor spiradoline single-doseANC Was signi? ditioning Responses in a Black-White Shuttle-Box cantly altered from those of the saline-pretreated subjects. The use of loW ANC dose levels of the agonists in the CRD [0130] The folloWing study demonstrates that the kappa tests (M.P.E. of approximately 20%) may have compromised opioid receptor agonist-induced adverse side effect dysphoria the extent of antagonism rather than optimize synergistic can be counteracted by activation of mu-opioid receptors, and ANC interactions of the tWo agonists as intended. Other pos fentanyl-induced euphoria is reciprocally counteracted by sible explanations for such complex opioid interactions are activation of kappa-opioid receptors. discussed beloW. [0131] Male Sprague-DaWley adult rats, Weighing 220 g to [0127] It is theorized that failure of [3-FNA pretreatment to 350 g, Were divided into four groups of 6 each (denoted as alter ANC of fentanyl in the CRD (as shoWn in FIG. 4) could Groups A, B, C, and D). The rats Were trained for place occur by several mechanisms. One possible mechanism is preference and place aversion to the selective mu-opioid ago that a supra-spinally or spinally innervated mu-opioid recep nist, fentanyl, and the selective kappa1-opioid agonist, spira tor link may exert tonic inhibitory control over spinal kappa doline, respectively. Group A received only saline subcuta opioid-agonist mechanisms, resulting in a blockade of the neous injections (placebo) throughout the study. Group B Was mu-opioid receptors by [3-FNA. The blocking of the mu trained and tested on three dose levels of fentanyl before receptors then could result in disinhibition of the spinal kappa testing, then trained on combined agonists before the last test. mechanism, and ANC Would be induced by release of an Group C Was trained on tWo doses of fentanyl before Tests 1 endogenous kappa-opioid receptor agonist. LikeWise, the and 2, then trained on tWo doses of spiradoline before Tests 3 decreased ANC of spiradoline after [3-FNA could relate to and 4, and ?nally trained on combined agonists before the last chronic supra-spinal or spinal kappa-opioid mechanisms acti test. Group D Was trained ?rst on three dose levels of spira vating release of an endogenous mu-opioid agonist. The doline before testing, then trained on the combined agonists resulting mu-opioid receptor agonist then Would inhibit spi before Test 5. nal pain-projection neurons reacting to incoming distal noci ceptive stimuli. Spiradoline Would still release endogenous [0132] The drug dose levels Were chosen from antinocice mu-opioid receptor agonist, but [3-FNA blockade of post ptive dose-response patterns of previous studies using the junctional mu-opioid receptors Would attenuate the ANC CWTF and CRD assays (Briggs et al., Pharmacol. Biochem. response. Behav. 60: 467-72 (1998); Briggs and Rech, 2008). Fentanyl citrate (Elkin-Sims, Inc., Cherry Hill, N.J., USA) doses for [0128] The interactions described above are consistent With the current study Were 0.003, 0.006, and 0.012 mg/kg. Spira the synergism of ANC by combined agonists in the saline doline doses Were 0.3, 0.6, and 1.2 mg/kg (Spiradoline Was pretreatment group (FIG. 4) being decreased after either generously provided by Dr. P. L. von Voigtlander, Upjohn antagonist pretreatment, [3-FNA or n-BNI. The greater Co., Kalamazoo, Mich., USA). Drugs Were dissolved in nor antagonism by n-BNI of the combined agonist ANC synergy mal saline and administered by subcutaneous (SC) injection. may indicate (as suggested by Schmauss etal.,Eu1: .1. Phar Fentanyl Was injected 15 minutes before placing subjects into macol. 135: 429-31 (1987) a dominant role of kappa-opioid the shuttle box, and spiradoline Was injected 30 minutes receptor mechanisms in the suppression of visceral pain. before placing subjects into the shuttle-box. The pretreatment Staahl et al., Pain. 123: 28-36 (2006) shoWed oxycodone to times Were based upon peak antinociceptive activities. The induce superior ANC vs. morphine in human subjects animals and procedures Were approved for this study, con exposed to experimental visceral nociception. Since oxyc forming to NIH standards, by the Michigan State University odone is a kappa-opioid receptor agonist metabolized to a Animal Use and Care Committee. mu-opioid receptor agonist (Ross et al., Pain. 84: 421-8 (2000), these results imply a combined mu- and kappa-opioid Place Conditioning Apparatus, Training and Testing Param interaction. eters [0129] Interactions betWeen exogenous mu- and kappa opioids, as Well as those betWeen endogenous opioids, seem [0133] TWo shuttle-boxes Were constructed With tWo com to be most implicated in conditions involving chronic visceral partments each, 35 cm long><13 cm Wide><13 cm high, joined pain. Several clinically-oriented revieWs have promoted the at the narroW Walls on one side, in Which 7 cm circles Were cut concept of employing opioid drug combinations for one centimeter above the ?oors. In each box, one compart improved therapeutic management of pain While reducing ment Was painted black With a mesh ?oor and the other adverse drug side effects (Coop Amer. J. Pharm. Educ. 24: compartment Was painted White With a smooth ?oor. A rect 198-205 (2002); Smith, Pain Physician. 11: 201-14 (2008). angular baf?e-plate, black on one side and White on the other, Joshi et al., Curl: Rev. Pain. 4: 499-506 (2000) revieWed the Was inserted betWeen the connecting Walls to restrict a rat to