Eur Resplr J 1988, 1, 171-175
No effect of oral N-acetylcysteine on the bioavailability of erythromycin and bacampicillin
0. Paulsen*, L. Borgstrom"*, B. Kagedal***, M. Walder****
No effect of oral N-acetylcysteine on the bioavailability of erythromycin and • Department of Clinical Phannacology, Lund bacampicillin. 0. Paulsen, L. Borgstrom, B. Kdgedal, M. Walder. University Hospital. ABSTRACT: In vitro studies with N-acetylcysteine (NAC) solutions used for •• Pharmacokinetics Laboratory, AB Draco, inhalation treatment have demonstrated inactivation of some antibiotics by Lund. ••• Department of Clinical Chemistry, Linkop NAC. Oral NAC treatment is increasingly common for long-term prophylaxis ing University Hospital. in chronic bronchitis. During exacerbations, treatment with oral antibiotics will •••• Department of Medical Microbiology, often be given simultaneously. We assessed the effect of simultaneous oral Malmo General Hospital, University of Lund, administration of NAC on the bioavailability of two antibiotics in ten healthy Sweden. volunteers. No effect of NAC was found on the bioavailability of ampicillin, after administration of the prodrug bacampicillin. A slight, but not significant Correspondence: 0. Paulsen, Department of statistical increase in erythromycin serum levels was seen with NAC. Acetylator Clinical Pharmacology, Lund University Hos phenotype did not influence the absorption of NAC, which seemed slightly pital, S-221 85 LUND, Sweden. reduced by bacampicillin, but significantly increased by erythromycin. No decrease of antibacterial activity of sera was found in vitro after the add.ition of Keywords: Acetylator phenotype; ampicillin; bacampicillin; drug interaction; erythromycin; NAC or the related thiol glutathione, employing micrococcus Juteus and glutathione; N-acetylcysteine. staphylococcus aureus as indicator organisms. Eur Respir J. 1988, 1, 171-175. Received: October 27, 1986; accepted after revision August 6, 1987.
N-acetylcysteine (NAC) has been used for more NAC on the antibacterial activity of sera against the than twenty years for inhalation treatment in lung indicator organisms, micrococcus luteus and staphy disease complicated by thick mucus secretions. Dur lococcus aureus. ing the last ten years oral NAC has also been effective as a mucolytic agent [7, 10] and extensive trials with Subjects and methods continuous medication have shown reduction of the exacerbation rates in patients with chronic bronchitis The study was approved by the local Ethics [2, 12]. During exacerbations, antibiotic treatment is Committee and performed in accordance with the usually instituted. Declaration of Helsinki. It was executed as an open In earlier studies on inhalation treatment with comparison of antibiotic and NAC concentrations NAC, inactivation of certain antibiotics occurred with simultaneous or separate administration of the when they were added to the NAC solution [6, 9]. No drugs. reduction of antibacterial activity occurred when antibiotics were given orally or intramuscularly Subjects during inhalation treatment [9, 14]. Ten healthy volunteers, five men and five women, Interaction studies between oral NAC and antibiot participated in the study. They were 30-45 years old ics have demonstrated no NAC influence on the and they weighed 55-91 kg. Physical examinations bioavailability of amoxicillin and doxycyclin, reduced and laboratory tests were carried out at least one absorption of cefalexin, and no decisive effects of week before the start of the study. No medication erythromycin [5, 11]. Interaction with ampicillin beside the test drugs and no alcoholic beverages were esters has not been studied, although the beta-lactam allowed during the study or during the preceding ring is susceptible to thiol attack and penicillins week. In all subjects the acetylator phenotype was consequently might be expected to interact with determined as previously described [13], to evaluate NAC. In vitro studies have indicated that an the possible influence of N-acetyltransferase on endogenous, related thiol compound, glutathione, deacetylation ofNAC. Two of the women and four of may bind to beta-lactam antibiotics, e.g. ampicillin, the men were found to be rapid acetylators. under physiological conditions (17, 18]. We have investigated the bioavailability after oral, Investigational drugs concomitant administration of NAC and erythromy cin base or bacampicillin, in healthy volunteers. We All drugs were administered in a commercially also assessed the possible influence of glutathione and available form. NAC was given as effervescent tablets 172 0. PAULSEN ET AL.
1 (Mucomyst® 0.2 g), erythromycin as erythromycin limits were 0.10- 100 j.lg•ml - . The inter- and intraas base enterocapsules (Ery-Max® 250 mg) and bacam say variation was ± 10%. picillin as plain tablets (Penglobe® 800 mg). Pharmacokinetic calculations Procedure Maximal plasma concentration (Cma.) was defined Initially NAC was given for five days, 600 mg b.i.d., as the highest experimental plasma concentration at 08 arid 20 h. At each occasion the three NAC obtained, and tmax was the time for Cmax· The area tablets were dissolved in 200 ml of tap water. On the 1 under the plasma concentration vs time curve (C,t 6 b study day, after overnight fasting, a final dose of curve) (AUC), was calculated according to the NAC, 600 mg, was given and blood for NAC analysis trapezoidal rule. All AUCs were calculated over the was sampled from an antecubital vein at the following first 12 h. The area under the first moment of the C,t scheduled times: 0, 20, 40 min, I , 1.5, 2, 3, 4, 6, 8, I 0 curve (AUMC) was calculated accordingly. Mean and 12 h after administration. Two hours after drug residence time (MRT) is the mean time for drug intake, a standardized breakfast was served [3]. Urine molecules to transit through the body and was was sampled as one pool 0-12 h for determination of calculated as AUMC/AUC. NAC. Renal clearance, CLR, of NAC was calculated as At another occasion, after a washout period of at the amount of NAC excreted in urine, corrected for least three days, two tablets of bacampicillin (1600 an endogenously excreted amount, divided by AUC mg) or four capsules of erythromycin (1000 mg) were for the 0- 12 h interval. administered with 200 ml of tap water in the same way as with NAC and with standardized breakfast and blood sampling for determination of antibiotic Statistical analysis concentrations at the same intervals. In the in vivo studies, evaluations were made by After another washout period, medication with analysis of variance and two-sided paired Student's t NAC effervescent tablets was reinstituted with three test. Level of significance was set at p < 0.05. tablets (600 mg) administered every morning fo r seven days. On the final day, erythromycin or In vitro experiment bacampicillin was administered concomitantly with the last NAC dose, and blood for NAC analysis and From a previous study, serum samples had been antibiotic concentrations was sampled at the time obtained from six healthy volunteers who had each intervals stated above. As previously, urine was received 2 g of ampicillin intravenously. Serum co1lected 0- 12 b after drug intake for NAC determi samples were taken before infusion, directly after nation. The differing dosing regimens for the repeated infusion and after 30 min and 1, 1.5 and 2.5 h. In a dosing of NAC do not influence the calculated similar way, sera containing erythromycin after the phannacokinetic values, because of the short elimina single-dose administration of this drug were obtained tion half-life of NAC [4). from the present experiment, before antibiotic admin istration and after 1, 1.5, 2, 3, 4, 6, 8 and 12 h. Each NAC determinations antibiotic-containing sample was divided into four Plasma samples were analysed by HPLC for parts. One was assayed for antibiotic concentration concentration of non-protein-bound NAC according and thiol-containing sera were added to the other to previously described methods [8]. Urine was three parts. To allow for sufficient interaction time, appropriately diluted and NAC was determined by a sera were kept for I h before bioassay. procedure similar to that used for plasma NAC determinations. Thiol sera The sera were obtained from healthy volunteers. Antibiotic determinations NAC was added in a concentration of 60 J.lmol·l- 1 A microbiological assay, using the agar well and 2 mmol· r 1 and glutathione in a concentration of 1 system, was deployed using disposable 24 x 24 em 1 mg · ml- . After addition of equal parts of anti plates with 125 m1 DST agar (Oxoid CM 261). Wells biotic-containing sera, the resulting thiol concentra with a diameter of 4 mm were made with a regular tions were chosen to correspond to or exceed levels hole punch machine. obtainable in vivo in the two principal situations For ampicillin, the indicator organism was micro where NAC treatment is instituted, namely for coccus luteus A TCC 9341 in the in vivo part of the prophylaxis in chronic bronchitis, and as an antidote investigations, and S. aureus 6-105 in the in vitro part. in paracetamol poisoning. The NAC concentrations Antibiotic standards and all samples were run in after admixture were 30 J.lmol· r I and I mmol· r I, 1 duplicate. Limits of the assay for ampicillin were respectively. The glutathione level, 500 jlg • ml- , was 1 0.05-400 J,lg•ml - . chosen to correspond to concentrations in whole For erythromycin, the indicator organism was blood, which greatly exceed those in serum. Thiol sera micrococcus luteus ATCC 9341 in both the in vivo were: tested and found to be without antibacterial and the in vitro part of the investigation, and the assay activity. BJOAVATLABILITY OF N-ACETYLC YSTEINE 173
Table I.- Pharmacokinetic parameters for ampicillin and erythromycin after oral dosing with and without simultaneous NAC medication c l AUC MRT .lllOX mg"'""·/ h mg·h·i1 h
Mean ampicillin 14.2 1.18 35.4 2.2 so 10.3 0.35 18.6 0.2
Mean ampicillin +NAC 11.5 1.00 31.5 2.3 so 3.9 0.30 9.5 0.1
Mean erythromycin 4.9 3.4 22.1 5.1 so 2.3 1.2 13.8 0.6
Mean erythromycin + NAC 6.0 3.5 25.1 5.0 so 4.0 0.5 14.4 0.4
Cmu: highest experimental plasma concentration; tmax: time for ClllU; AUC: area under the plasma concentration vs time curve; MRT: mean residence time.
Results 14 Pharmacokinetics of antibiotics After a single dose of antibiotic, none of the 12 pharmacokinetic parameters for the antibiotics ob ~- ~ 10 served differed from those obtained with concomitant E NAC administration (table I, figs I and 2). 0 c e Mean serum levels of ampicillin were slightly lower 0 0 with NAC co-medication. One individual demon E :J 6 strated extremely high em .. for ampiciUin after single ~ dose medication, with a correspondingly high AUC. "' 4 With concomitant NAC, Cmax in this subject was ·~a 1 , ·a reduced from 42.8 to 21.4 mg·r and AUC E 1 2 decreased from 87.3 to 53.0 mg · h · r . When this < subject was excluded, mean cmax in the remaining nine subjects was J 1.0 mg · r 1 without, and I 0.4 0 0 2 4 6 e 10 12 mg·/- 1 with NAC co-medication. Mean AUC was 1 the same, 29.6 and 29. 1 mg·h·r . Thus, NAC did Time ( Hours ) not seem to influence the pharmacokinetics of Fig. 2. e: mean serum levels of ampicillin after administration of bacampicillin (table I, fig. 2). bacampicillin; 0 : mean serum levels of ampicillin after simultane ous administration of bacampicillin and NAC. The differences are 6 not statistically significant with respect to AUC, Cmu• tm.. and MRT.
~ 5 E
~ 4 Erythromycin absorption showed a large interindi E vidual variation with a cmax ranging from 2.1 to 8.5 :J ~ 3 (mean 4.9) mg·r' after erythromycin single dose "'c administration. With concomitant NAC, the range ·g_ 2 1 E was 2.2 to 15.1 (mean 6.0) mg · r . Similar tmax values
J:e were obtained for erythromycin with and without >. 1 concomitant NAC, 3.4-3.5 h. MRT was fairly w constant, 4.0- 5.5 h (mean 5.1) without and 4.3-5.6 h (mean 5.0) with NAC co-medication. AUC for 2 4 6 8 10 12 erythromycin increased in seven out of ten subjects, 1 Time (Hours) from mean 22. I to 25.1 mg · h · r . Cmax of erythromy cin was higher in seven out of ten subjects with NAC, Fig. l. e: mean serum levels of erythromycm given as single drug; 0 : mean serum levels of erythromycin with simultaneously and also in two of the three subjects without increased administered NAC. The differen ce.~ are not statistically significant AUC, but the difference was not statistically signifi with respect to A UC, C.,. ,. 1.,.. and M RT. cant. 174 0. PAULSEN ET AL.
Table II.· Pharmacokinetic parameters for oral NAC given with and without oral antibiotic medication
t AUC MRT CLR c DIU IIW< j.lmOl·l"1 h IJ.mol·h·t 1 h l·h·kg'1
MeanNAC 13.62 0.68 23.03 2.31 0.053 SD 6.0 0.36 6.25 0.39 0.011
Mean NAC +Ampicillin 10.93 0.72 20.95 2.65 0.057 so 6.07 0.37 6.80 0.39 0.019
Mean NAC + Erythromycin 18.92 0.63 27.73 2.46 0.066 SD 13.22 0.51 11.74 0.43 0.023
Cm&X: highest experimental plasma concentration; tlllAl<: time for ClllAl<; AUC: area under the plasma concentration vs time curve; MRT: mean residence time; CLR: renal clearance
1 N A C disposition and AUC (20.951J.mol· h · /- ) ofNAC with bacampi cillin co-medication was found to be highly significant No correlation was found between acetylator when compared with levels of NAC given with phenotype and plasma levels or the bioavailability of erythromycin (p
Discussion 2. Boman G, Backer U, Larsson S, Melander B, Wahlinder L. Oral acetylcysteine reduces exacerbation rates in chronic bronchi In the present investigation of an in vitro model we tis: report of a trial organized by the Swedish Society for could not confirm the earlier reported binding Pulmonary Diseases. Eur J Respir Dis, 1983, 64, 405-415. between glutathione and ampicillin [17], and no effect 3. Borgstrom L, Johansson C-G, Larsson H, Lenander R. - ofNAC was seen at either high or low concentrations. Pham1acokinetics of bcndroflumethiazide after low oral doses. J Pharmacokinet Biopharm, 1981, 9, 4, 431-441. Additionally, no reduction of the anti-bacterial 4. Borgstrom L. Kagedal B, Paulsen 0 . - Pharmacokinetics ofN activity of erythromycin from thiols was found. acetylcysteine in man. Eur J Clin Pharmacol, 1986, 31, 217- 222. Accordingly, the in vivo results demonstrated a Jack 5. Ferrari V. - Safety and drug interactions of oral acetylcysteine of adverse effects of NAC towards ampicillin, the related to utilization data. Eur J Respir Dis, 1980, 6l(suppl III), absorption of which was unaffected. However, signifi 151- 157. 6. Gottschalk B, Wichmann G. - Die Wirkung von N-acetyl-L· cantly less NAC was absorbed with ampicillin co cysteine (Mucosolvin•) auf vcrscbiedene Antibiotika. Dtsch Ge medication than with erythromycin. An absorption sundh, 1970, 25, 700-702. interaction between two drugs might be expected to 7. Grassi C. Morandini GC.- A controlled trial of intermittent affect the availability of both. However, if both drugs oral acetylcysteine in the long term treatment of chronic bronchitis. Eur J Clin Pharmacal, 1976, 9, 393- 396. utilize the same transport mechanism, but have 8. Kagcdal B, Kiillberg M, Martensson J. - Determination different affinity constants, only one of the drugs might of non-protein-bound N-acetylcysteine in plasma by high be affected within a certain concentration interval. perfo.nnance liquid chromatography. J Chromatogr, 1984, 311, Recent studies indicate a dose-dependent absorption 170- 175. of bacampicillin and the existence of a capacity-limited 9. Lawson D, Saggers BA. - N.A.C. and antibiotics in cystic fibrosis. Br Med J, 1965, I, 317. transport system in the human intestine for aminopen 10. Lemy-Delois N, Frigerio G , Lualdi P. - Oral acetylcysteine in icillins [15, 16]. The natural substrate for a specialized bronchopulmonary disease. Comparative clinical trial with brom transport process is an endogenous substance, and hexine. Acta Therapeutica, 1978, 4, !25- 132. drugs utilizing such processes should be similar in II. Lualdi P, Marca G. - Effect de Ia n-acetylcysteine orale sur Ia biodisponibiliti: des antibiotics chez l'homme. Ars Medici, 1979, 34, chemical structure. The penicillin nucleus is thought to 8, 761 - 769. be derived from L-cysteine and valine, and aminopeni 12. Multicenter Study Group (1980). - Long-term oral acetylcys cillins may have di-peptide-like structures. tcine in chronic bronchitis. A double-blind control study. Eur J A recent review article has discussed transport Respir Dis, 1980, 6J(suppl. II), 93- 108. systems for the precursor amino acids of the NAC 13. Paulsen 0, Hoglund P, Nilsson L-G, Gredeby H. - No interaction between H 2 blockers and isoniazid. Eur J Respir Dis, related thiol, glutathione [1), and such amino acids can 1986, 68, 286-290. be formed from NAC. The absorption ofNAC is rapid, 14. Saggers BA, Lawson D. - Some observations on the but the oral availability is only about I 0% [4]. Since the penetration of antibiotics thro·ugh mucus in vitro. J Clin Pathol, oral availability of ampicillin esters is much higher, 1966, 19, 313- 317. 15. Sjovall J, Alvan G, Westerlund D. - Dose-dependent absorption of NAC could be reduced if NAC has to absorption of amoxicillin and bacampicillin. Clin Pharmacal Ther, compete with ampicillin for the same transport system. 1985, 38, 241 - 250. In the case of erythromycin, no decrease of serum 16. Sjovall J, Alvan G, Westerlund D.- Oral cyclacillin interacts levels was found with NAC, but rather a tendency to with the absorption of oral ampicillin, amoxicillin and bacampicil increased concentrations that was not statistically lin. Eur J Clin Pltarmacol, 1985, 29, 495- 502. 17. Squella JA, Nunez-Vergara U. - Interactions between significant. glutathione and ampicillin: an a.c. polarographic method. Biochem On the other hand, there was an increased Bioenergetics, 1983, II, 265-271. availability of NAC when given together with 18. Squella JA, Nunez-Vergara U, Barria J, Echegaray E. - In erythromycin as compared with that found with vitro binding between glutathione and cloxacillin by a.c. polarogra ampicillin co-medication. The antibiotics may differ phy. Biochem Bioenergetics, 1983, 11, 425-433. in their effects on bacteria that can effect deacetyla tion of drugs in the gut before absorption. Alterna RESUME: Des etudes in vitro avec des solutions de N tively, the fraction of first pass metabolism of NAC acetylcysteine utilisi:es pour inhalation, ont demontri: !'inactivation that occurs in the liver through oxidative pathways de certains antibiotiques par la N-acetylcysteine. Les traitements oraux a base de N-acetylcysti:ine sont de plus en plus courants pour might marginally be inhibited by erythromycin, but it Ia prophylaxic a long terme dans Ia bronchite chronique. Au cours is unlikely to be influenced by ampicillin. des exacerbations, le traitement avec des antibiotiques oraux sera Thus, the present investigation does not indicate souvent donne concomitamment. Dans cette etude, nous avons any need for a change in dosage or of choice of i:tudii:, chez dix volontaircs sains, l'effet sur Ia biodisponibilite de !'administration orale simultanee de deux antibiotiques et de IaN antibiotic when treatment with erythromycin or acetylcysteine. L'on o'a trouvi: aucun effet de Ia N-acctylcysteine bacampicillin is considered in patients with ongoing sur la biodisponibilite de l'ampicilline, apre·s administration de Ia treatment with NAC. Also, since addition of these 'prodrug' bacampicilline. L'on a observe une augmentation Iegere, antibiotics does not reduce the bioavailability of mais statistiquemcnt non significative, des niveaux si:riques NAC, no change of dosage of NAC seems indicated. d'erythromycinc avec Ia N-acetylcysti:ine. Le phenotype d'acetyla· tion n'infiuence pas !'absorption de Ia N-acetylcysteine, qui scmblait li:gerement rectuite par Ia bacampicillinc, mais par contre References significativement augmenti:e par l'i:rythromycine. Si l'on emploie Micrococcus !ulcus et Staphylococcus aureus comme organismes I. Bannai S, Tateishi N. - Role of membrane transport in indicateurs, l'on n'a pas trouvi: de diminution de l'activite anti metabolism and function of glutathione in mammals. J Mem Bioi, bacti:rienne du serum in vitro apres administration de N· 1986, 89, 1-8. acetylcysteine ou du thiol parent, Ia glutathione.