INTERNATIONAL JOURNAL OF IMMUNOI'ATIIOLOGY AND I'IIARMACOLOGY Vol. 16, no. 3, 207·214 (2003) REVIEWARTICLE METADOXINE IN THE TREATMENT OF ACUTE AND CHRONIC ALCOHOLISM: A REVIEW G. ADDOLORATO, C. ANCONA, E. CAPRISTO and G. GASBARRINI Institute ofInternal Medicine, Catholic University ofRome, Italy Received February 27, 2003 - Accepted August 5, 2003 Alcohol abuse and alcoholism are responsible for a wide variety of medical problems. The pharmaco­ therapeutic aspect of alcoholism includes the use of drugs, with different actions and objectives. Among them, metadoxine seems to be of interest. Metadoxine is able to accelerate the elimination of alcohol from the blood and tissues, to help restore the functional structure of the liver and to relieve neuro-psychological disorders associated with alcohol intoxication. Metadoxine also seems to be safe; in more than 15 years of post-marketing surveillance only minor aspecific and reversible events were monitored in patients exposed to the treatment. In this review the preclinical and clinical results obtained using metadoxine in acute and chronic alcohol intoxication are reported. Alcoholism is a multifactorial disorder in which major contributing factors to road accidents, suicide biologic and genetic factor interact along withcultural and violent death in young adults (11). and social factors (1,2). Alcohol addiction represents The pharmaco-therapeutic aspect of alcoholism a social problem and a relatively common disease of includes the use of drugs, with different actions and western countries like Europe and the USA. From 20 objectives (12). Among them, metadoxine seems to to 40% of subjects admitted to hospitals have alcohol­ be of interest. The present review evaluates the related problems (3) and in elderly people alcohol­ pharmacology and the therapeutic use ofmetadoxine related disorders represent as frequent a reason for (figure I), a drug promoted for the treatment of acute hospitalization as myocardial infarction (4). and chronic alcohol intoxication and alcoholic liver The most lasting damaging actions of ethanol disease. are exerted on the liver function and structure (5). A liver disease is often present in patients affected by Enzymatic activity ofMetadoxine compounds alcohol abuse and/or alcoholism; however the Metadoxine is formed by the salification of two mechanisms responsible for the liver toxicity of components, pyrrolidone carboxylic acid (PCA) and ethanol are still not completely understood (6). pyridoxol, in a single product. PCA is usually present Ethanol also modifies the GABA-mediated in the diet and produced endogenously by enzymatic neurotransmission (7). Probably it preferentially conversion of the gammaglutamyl amino acids to stimulates the dopaminergic transmission in the PCA and free amino acids in several mammalian mesolimbic system (8), interferes withserotoninergic tissues, including the central nervous system, where transmission (9) and with the release of glutamate in ithasaroleinthecompositionof neuroactivemolecules the central synapses (10). The neuropathological (13). PCA is an intermediate in the gammaglutamyl manifestations usually appear after many years of cycle, it is transformed into glutathione by two excessive drinking. In addition to the effects of subsequent reactions catalyzed by gamma­ alcohol on the nervous system, it may be one of the glutamylcysteinesynthetaseandglutathion synthetase Key words: nietadoxine, alcoholism, acute and chronic alcohol intoxication Mailing address: Dr. Giovanni Addolorato 0394-6320 (2003) Institute of lnterrnal Medicine, Catholic University of Rome Copyright © hy BIOLlFE, s.a.s.. This publicationand/urarticle is fur individualusc only and may not he further Largo A.Gemelli 8,00168 Rome, Italy. reproduced without writtenpermission fromthecopyright holder. Phone +39-06- 30154334. Fax +39-06-35502775 Unauthorized reproduction mayresultin financial amiotherpenalties e-mail: g.addoloratotsm.unicau.it 207 208 G. ADDOLORATO ET AL. respectively, and its production is linked to the probably synthesised via the g-glutamil cycle. (21). gammaglutamyl transferase activity of the liver cell Excretionoccursapproximatelyinthesameproportion membraneandto hepaticlevelsof reducedglutathione through the urine and the feces, between 40 and 45% (GSH) (14).It hasalso beenshownthatPCAfacilitates in 24 hours in the urine, and between 35 and 50% in ATP synthesis by stimulating the "de novo" synthesis 96 hours in the feces (21). This information justifies of the purine nucleotide. (15). Pyridoxol is aprecursor the dosage scheme recommended for the therapeutic of coenzymes such as pyridoxal phosphate which use in humans. accelerates the metabolic degradation of ethanol and prevents ATP inactivation by acetaldehyde, the main Preclinical studies ethanol metabolite (16). Metadoxine has been shown to induce profound In Metadoxine PCA and Pyridoxol are linked by alterations of alcohol metabolism in rats. It increases salification and in this form their pharmacological the activity of acetaldehyde dehydrogenase and properties seem to be synergic as shown by their preventsthedecreaseinalcoholdehydrogenaseactivity superior activity when given together, with respect shown in chronic ethanol fed rats (22,23). Its to separate administration (17,18). administration accelerates plasma and urinary clearance of ethanol and acetaldehyde in a dose­ Pharmacokinetic profile dependent manner (22). The accelerated urinary Metadoxine exerts a metabolic effect, the clearance could be due to the inhibiting effect of efficiencies of which depend on the presence of both metadoxine on the formation of macroaggregates moieties, pyridoxine (PDX) and pyrrolidone between albumin and acetaldehyde shown in alcohol carboxylate (PCA); in the same tissue with the same treated rats. Metadoxine significantly inhibits the profile, and both in concentrations able to trigger the increase of fatty acid esters in the liver of ethanol metabolic biotransformations in which they are treated rats (24), restoring the correct ratio between implicated. Pharmacokinetic studies have been hepatic saturated and unsaturated fatty substances performedinrats,dogs,monkeyandhealthyvolunteers (25). At 160 mg/kg, Metadoxine also prevented the (\ 8-20). These studies mainly showed that the oral formation of fatty liver in 50% of rats exposed to a absorption ofthedrugisfast,withhighandreproductive dose of ethanol able to induce fatty liver in 100% of absolutebioavailability(60to80%)andwithextensive the rats in the control group (23). tissue distribution, as shown by the large apparent In normal untreated rats, Metadoxine has been distribution volume. The half-life is 40 to 60 minutes shown to increase hepatic ATP content through an without appreciable differences between oral or activation of the purine "de novo" synthesis (15,17), intravenous administration. The kinetic profile is and in hepatocytes of acutely and chronicaIly alcohol specific to metadoxine as such. The extemporaneous intoxicated rats it is able to restore the activity of the administration of the two individual components can aldehyde dehydrogenase and to increase the reduced not compete in terms of the blood concentration, thus glutathione levels (26). Pretreatment of animals with of tissue distribution and ultimately of therapeutic Metadoxine one hour before ethanol administration effect, with Metado·xine. produced significant protection against glutathione . This is the consequence of Metadoxine being an depletion and oxidoreductive stress in hepatic and ion-pair, and was very easily seen comparing the extrahepatictissue(27,28),andanincrementin alcohol kinetic profile of pyridoxine administered as a metabolism and turnover (25). Recently Metadoxine component of Metadoxine, with that of the same has been shown to prevent glutathione depletion, pyridoxine administered alone (21), which yields lipid peroxidation damage, coIlagen deposition and lower concentrations with a very long delay. TNF alf'a secretions induced by alcohol and The identified metabolites are those expected acetaldehyde in hepatocytes and hepatic steIlate ceIls from the metabolism of glutamate and of pyridoxine. (29) These mechanisms could be implicated in the In particular, the radioactivity given with metadoxine ability of Metadoxine to prevent hepatic wasfound in glutamate, glutamine, glutamylcysteine, necroinflammation, fibrosis and progression to glutathione, a-ketoglutarate, pyridoxal, pyridoxal cirrhosis in rats chronically exposed to hepatotoxic phosphate and pyridoxamine. Approximately 12% agents as shown in rat models of hepatic cirrhosis of total radioactivity wasfound inpeptide derivatives, (14,30) (Fig. 2). loL J. Immuoopalhol. Phanoacol. 209 OH Fig. 1. Chemical structure of metadoxine (pyridoxine L-2-pyrrolidone-5-carboxylate). (Modifiedfrom: Metadoxine. Drugs ofToday 1988; 24:217-219) N coo- H~ i H 60 , --------------------------- Fig. 2. Serum levels (Itg/ml: meanti:standarddeviations) of immunoreactive prolyl 50 hydroxylase (SIRPH). The CCL 4-treated animals have 40 significantly higher SIRPH than controls or rats protectedwith metadoxine. (Modified from: 30 AnnoniG, Contu L, Tronci MA, et al PyridoxolL, 2-Pyrrolidon­ 20 5 Carboxylate prevents active fibroplasia in CCl4-treated 10 ra~.PharmacoIRes1992,25 (1): 87-93) O -l-_ ---l ---L..__-.--__..L-__---l.__----.__...l- L-_ Controls CCl4 CCl4 treated with metadoxine Fig. 3. Proportion ofpatients who started to recover (decrease ofblood alcohol concentration by at least one category) from