dextrorphan and Chemical-and-Drug-Induced-Liver-Injury

The influence of genetically determined oxidation polymorphism on drug hepatotoxicity has been poorly investigated and results are controversial. We studied drug oxidation capacity in 51 patients with hepatitis caused mainly by drugs undergoing oxidative metabolism, using dextromethorphan, a test compound recently proposed as a substitute for debrisoquine. Phenotyping was performed using the metabolic ratio (MR) calculated as MR = 0-10 h urinary output of dextromethorphan/0-10 h urinary output of dextrorphan (the main oxidative metabolite), after oral administration of 40 mg dextromethorphan hydrobromide. Dextromethorphan oxidation capacity was similar in patients and in 103 control subjects as judged by: (a) the prevalence of each phenotype (5.9% versus 3.9% for the poor metabolizer phenotype and 94.1% versus 96.1% for the extensive metabolizer phenotype; (b) the frequency distribution histograms of log metabolic ratio; (c) the mean values of dextromethorphan and dextrorphan urinary outputs and of log metabolic ratio for each phenotype. These results show that hepatotoxicity of several drugs, including amineptine, amodiaquine and Plethoryl, is related neither to an impairment in dextromethorphan oxidation capacity nor to an unusually high capacity to oxidize this drug.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Chemical and Drug Induced Liver Injury; Cohort Studies; Dextromethorphan; Dextrorphan; Female; Humans; Levorphanol; Male; Middle Aged; Oxidation-Reduction; Phenotype; Polymorphism, Genetic

Amineptine-induced immunoallergic hepatitis is unpredictable. It may be related to its oxidation into a reactive metabolite acting as hapten. We have looked for a possible genetic predisposition involving drug oxidation capacity and/or cell defense mechanisms in nine patients with previous amineptine hepatitis. Drug oxidation capacity was assessed using dextromethorphan, a test compound recently proposed as a substitute for debrisoquine. The eight patients tested had the extensive metabolizer phenotype. The susceptibility to amineptine metabolites was studied by an in vitro test assessing the destruction of the patients' lymphocytes by reactive metabolites generated from amineptine by a standardized oxidation microsomal system. Lymphocyte death increased with the dose of amineptine (1 to 2.5 mM); it was increased by preincubation with trichloropropene oxide, but was absent when amineptine was omitted or when the oxidation system was not operating. Mean lymphocyte death was twice higher in the nine patients with amineptine hepatitis than in 17 healthy controls. In contrast, when the test was performed with acetaminophen (3 to 10 mM), lymphocyte death was similar in controls and in patients. Basal epoxide hydrolase activity toward benzo[a]pyrene-4,5-oxide and glutathione concentration was similar in lymphocytes from controls and patients. Family studies showed an increased susceptibility to amineptine metabolites in lymphocytes from several first-degree relatives of two patients. These results show that amineptine hepatitis occurs in patients with extensive dextromethorphan oxidation capacity but with an increased susceptibility to amineptine reactive metabolites, probably related to a genetic deficiency in a cell defense mechanism.

Topics: Adolescent; Adult; Antidepressive Agents, Tricyclic; Cell Survival; Chemical and Drug Induced Liver Injury; Dextromethorphan; Dextrorphan; Dibenzocycloheptenes; Family Health; Female; Humans; Lymphocytes; Male; Middle Aged; Oxidation-Reduction; Phenotype