Acute and chronic drug-induced hepatitis

Hydralazine-induced liver injury: a review and discussion

Hydralazine is a commonly prescribed antihypertensive agent. Some of its labelled adverse reactions include lupus-like syndrome, tachycardia, headache and fever. Despite its well-known side effects, little is known about hydralazine's hepatotoxic effects. We report the case of a 54-year-old female patient who was started on hydralazine for hypertension management but later presented with hydralazine-induced liver injury. Her initial presentation consisted of non-specific symptoms and a hepatocellular injury pattern. Liver biopsy revealed hepatic steatosis. Three weeks after discontinuation of hydralazine, the patient's liver enzymes normalised, and her symptoms resolved. Few studies have examined the incidence and mechanism by which hydralazine induces a liver injury pattern. With this case, we review the literature, the pathogenesis involved and the eventual management of hydralazine-induced liver injury. We propose close monitoring of liver enzymes for patients on hydralazine throughout their treatment course.

Valproic Acid-Induced Liver Injury: A Case-Control Study from a Prospective Pharmacovigilance Program in a Tertiary Hospital

Introduction: Valproic acid (VPA) is an antiepileptic drug extensively used for treating partial and generalised seizures, acute mania and as prophylaxis for bipolar disorder. Drug-induced liver injury (DILI) persists as a significant issue related to fatal outcomes by VPA. The aim of this study was to increase our knowledge about this condition and to better identify patients affected. Methods: We conducted an observational retrospective case-control study that identified cases of DILI by VPA from the Pharmacovigilance Programme from our Laboratory Signals at La Paz University Hospital from January 2007 to December 2019. From the Therapeutic VPA Monitoring program, two control groups were assigned, VPA-tolerant patients and the other with patients who developed mild VPA-related liver injury but who did not meet the DILI criteria, matched for date, age and sex. Results: A total of 60 patients were included in the study: 15 cases of DILI, 30 VPA-tolerant controls and 15 controls with mild liver injury. Mean age for the cases was 45.7 years, 4 (26.7%) were women and 5 (33.34%) were children under 18 years, of them 3 (20%) were fatal. Polytherapy with other antiepileptic drugs (p = 0.047) and alcohol consumption (p < 0.001) were associated with a greater risk of developing DILI by VPA. A diagnosis of epileptic seizure was more frequently related to DILI when compared with the VPA-tolerant controls (p < 0.001). The cases developed hepatocellular liver injury (p < 0.001), while the mild hepatic damage controls had a higher rate of cholestatic liver injury (p < 0.001). The laboratory lactate dehydrogenase values were statistically higher (even at baseline) in patients with DILI than in both control groups (p = 0.033 and p = 0.039). Conclusions: VPA hepatotoxicity remains a considerable problem. This study offers interesting findings for characterising VPA-induced liver injury and at-risk patients.

Computational Models Using Multiple Machine Learning Algorithms for Predicting Drug Hepatotoxicity with the DILIrank Dataset

Drug-induced liver injury (DILI) remains one of the challenges in the safety profile of both authorized and candidate drugs, and predicting hepatotoxicity from the chemical structure of a substance remains a task worth pursuing. Such an approach is coherent with the current tendency for replacing non-clinical tests with in vitro or in silico alternatives. In 2016, a group of researchers from the FDA published an improved annotated list of drugs with respect to their DILI risk, constituting “the largest reference drug list ranked by the risk for developing drug-induced liver injury in humans” (DILIrank). This paper is one of the few attempting to predict liver toxicity using the DILIrank dataset. Molecular descriptors were computed with the Dragon 7.0 software, and a variety of feature selection and machine learning algorithms were implemented in the R computing environment. Nested (double) cross-validation was used to externally validate the models selected. A total of 78 models with reasonable performance were selected and stacked through several approaches, including the building of multiple meta-models. The performance of the stacked models was slightly superior to other models published. The models were applied in a virtual screening exercise on over 100,000 compounds from the ZINC database and about 20% of them were predicted to be non-hepatotoxic.

Relevance of Liver Failure for Anti-Infective Agents: From Pharmacokinetic Alterations to Dosage Adjustments

The liver is a complex organ with great ability to influence drug pharmacokinetics. Due to its wide array of function, its impairment has the potential to affect bioavailability, enterohepatic circulation, drug distribution, metabolism, clearance, and biliary elimination. These alterations differ widely depending on the cause of the liver failure, if it is acute or chronic in nature, the extent of impairment, and comorbid conditions. In addition, effects on liver functions do not occur in a proportional or predictable manner for escalating degrees of liver impairment. The ability of hepatic alterations to influence PK is also dependent on drug characteristics, such as administration route, chemical properties, protein binding, and extraction ratio, among others. This complexity makes it difficult to predict what these effects have on drugs. Unlike certain classes of agents, efficacy of anti-infectives is most often dependent on fulfilling pharmacokinetic/pharmacodynamic targets, such as C_max/MIC, AUC/MIC, T_>MIC, IC₅₀/EC₅₀, or T>EC₉₅. Loss of efficacy, or conversely, increased risk of toxicity may occur in certain circumstances of liver injury. Although important to consider these potential alterations and their effects on specific anti-infectives, many lack data to constitute specific dosing adjustments, making it important to monitor patients for effectiveness and toxicities of therapy.

The mechanistic basis for the induction of hepatic steatosis by xenobiotics

INTRODUCTION

Hepatic steatosis is the histological observation of numerous lipid inclusions due to an excess accumulation of triacylglycerols. They are a concern with new therapeutic candidates because they signify altered lipid metabolism that can progress to more serious liver toxicity.

AREAS COVERED

This article is based on an article search using the PubMed database from 1987 to 2011 and confirms associations for several previously marketed drugs with four basic hepatocellular mechanisms. The article also describes how these mechanisms are controlled by master regulators of lipid metabolism, which include gene transcription factors, nuclear receptors, hormonal signaling, energy sensing proteins, endoplasmic reticulum stress signaling and certain key metabolic intermediates.

EXPERT OPINION

Drug-induced hepatic steatosis is typically not detectable by conventional means other than invasive histological examinations. By understanding the basic mechanisms, key regulators and energy signaling systems of the liver, the investigator is better equipped to avoid xenobiotics with steatogenic potential in the drug discovery or early development process. There are now a number of methods for detecting this potential, specifically gene expression or metabolomic profiling and pathway analysis or mechanism-based in vitro systems.

Biochemical mechanisms in drug-induced liver injury: Certainties and doubts

Drug-induced liver injury is a significant and still unresolved clinical problem. Limitations to knowledge about the mechanisms of toxicity render incomplete the detection of hepatotoxic potential during preclinical development. Several xenobiotics are lipophilic substances and their transformation into hydrophilic compounds by the cytochrome P-450 system results in production of toxic metabolites. Aging, preexisting liver disease, enzyme induction or inhibition, genetic variances, local O₂ supply and, above all, the intrinsic molecular properties of the drug may affect this process. Necrotic death follows antioxidant consumption and oxidation of intracellular proteins, which determine increased permeability of mitochondrial membranes, loss of potential, decreased ATP synthesis, inhibition of Ca²⁺-dependent ATPase, reduced capability to sequester Ca²⁺ within mitochondria, and membrane bleb formation. Conversely, activation of nucleases and energetic participation of mitochondria are the main intracellular mechanisms that lead to apoptosis. Non-parenchymal hepatic cells are inducers of hepatocellular injury and targets for damage. Activation of the immune system promotes idiosyncratic reactions that result in hepatic necrosis or cholestasis, in which different HLA genotypes might play a major role. This review focuses on current knowledge of the mechanisms of drug-induced liver injury and recent advances on newly discovered mechanisms of liver damage. Future perspectives including new frontiers for research are discussed.

Acute and chronic hepatitis

Most liver biopsies performed today are for grading and staging of chronic viral hepatitis and steatohepatitis; there are uncommon indications for liver biopsy in the setting of acute hepatitis. Pathologists must have a broad knowledge of many forms of acute and chronic hepatitis, as well as their variations; these include viral hepatitis, autoimmune hepatitis, drug-induced hepatitis, metabolic diseases, and reactive hepatitis secondary to systemic disease processes. In this article, the authors review the pathological features of acute and chronic hepatitis.

Fulminant hepatic failure following halothane anaesthesia

The forensic pathologist is responsible for determining the cause, manner and approximate time of death and injury. After recording the detailed description of the external and internal appearances, a short summary should be offered of the major positive findings and their relationship to the cause of death. In many cases this will be obvious, however when the findings are less clear-cut, or are multiple, then the alternatives should be discussed detailing the possible sequence of events and interpreting the findings in concluding the cause of death. It is essential to causally connect the autopsy findings to the cause of death. We present a case report wherein a person who sustained avulsion injury to his left hand in an industrial accident, died due to, fulminant hepatitis, hepatic encephalopathy and acute renal failure, having undergone six operations under general anesthesia with halothane during his stay in the hospital.

METABOLIC ACTIVATION OF TROGLITAZONE: IDENTIFICATION OF A REACTIVE METABOLITE AND MECHANISMS INVOLVED

Troglitazone (TGZ), the first glitazone used for the treatment of type II diabetes mellitus and removed from the market for liver toxicity, was shown to bind covalently to microsomal protein and glutathione (GSH) following activation by cytochrome P450 (P450). The covalent binding of (14)C-TGZ in dexamethasone-induced rat liver microsomes was NADPH-dependent and required the active form of P450; it was completely inhibited by ketoconazole (10 microM) and GSH (4 mM). The covalent binding in P450 3A4 Supersomes (9.2 nmol of TGZ Eq/nmol P450) was greater than that with P450 1A2 (0.7), 2C8 (3.7), 2C19 (1.4), 2E1 (0.6), and 2D6 (1.1) and 3A5 (3.0). The covalent binding in liver microsomes from rats pretreated with dexamethasone (5.3 nmol of TGZ Eq bound/nmol P450) was greater than that from rats pretreated with vehicle (3.5), beta-naphthoflavone (0.4), phenobarbital (1.1), or pyridine (2.5). A TGZ-GSH adduct was detected by liquid chromatography-tandem mass spectrometry and radioactivity detection with a deprotonated quasi-molecular ion [M-H](-) at m/z 745, with fragment ions at m/z 438 (deprotonated TGZ moiety), and at m/z 306 (deprotonated GSH moiety). The TGZ-GSH adduct was determined to be 5-glutathionyl-5-[4-(6-hydroxy-2,5,7,8-tetramethylchroman-2-ylmethoxy)benzyl]-thiazolidine-2,4-dione based on collision-induced dissociation fragmentation, and one- and two-dimensional NMR analysis of the isolated adduct. The synthetic 5-hydroxy TGZ and the benzylidene derivative of TGZ did not react with GSH or GSH ethyl ester. The mechanisms for metabolic activation of TGZ may involve an ultimate reactive sulfonium ion which could be formed from an initial sulfoxide followed by a formal Pummerer rearrangement, or a C5 thiazolidinedione radical or a sulfur cation radical.

Hepatic oxidative alterations in patients with extra-hepatic cholestasis. Effect of surgical drainage

BACKGROUND/AIMS

The mechanisms of liver injury in conditions of biliary obstruction are poorly understood. Hepatic oxidative injury has been observed in experimental models of cholestasis. Little is known in humans. This study aimed to gain more insights into the hepatic redox status in human cholestasis.

METHODS

Liver concentrations of total glutathione, protein sulfhydryls and malondialdehyde (end-product of lipid peroxidation) were measured in hepatic specimens of 12 patients with obstructive jaundice before and after the application of an external biliary drainage and in six control subjects.

RESULTS

Compared to control subjects, biliary obstructed patients showed significantly (P < 0.001) lower concentrations of hepatic glutathione and protein sulfhydryls, and higher (P < 0.001) levels of malondialdehyde, in the presence of comparable protein concentrations. Two-weeks after the application of external biliary drainage, cholestatic indices were significantly improved and the observed changes in glutathione, protein sulfhydryls and malondialdehyde levels, significantly decreased.

CONCLUSIONS

This study shows that cholestasis is associated with a decreased protein and non-protein sulfhydryl content in the liver and with an increased lipid peroxidation. These alterations reversed almost completely after biliary drainage, indicating the cholestasis itself as the determining factor for the redox status impairment observed in the liver of patients with extra-hepatic biliary obstruction.

Systematic review of the efficacy and safety of perhexiline in the treatment of ischemic heart disease

Perhexiline was introduced about 30 years ago and rapidly gained a reputation for efficacy in the management of angina pectoris. However, hepatic and neurological adverse effects associated with perhexiline administration led to a marked decline in its use. The drug was originally classified as a coronary vasodilator, and later as a calcium channel antagonist, but recent data suggests that it acts as a cardiac metabolic agent, through inhibition of the enzyme, carnitine palmitoyltransferase-1 (CPT-1). Given the drug's unique anti-ischemic action and favorable hemodynamic profile, together with an improved understanding of the mechanisms underlying the adverse effects of the drug and the clear clinical need for additional therapies in refractory patients, perhexiline is currently being re-appraised as a potentially useful agent in the management of severe myocardial ischemia. Perhexiline is being considered for registration or re-registration in a number of countries and is being evaluated in a large-scale clinical trial in elderly patients with aortic stenosis and myocardial ischemia. This systematic review examines the evidence from available published literature in relation to the efficacy and tolerability of perhexiline in the treatment of cardiac disease. While there is a lack of well designed controlled trials using objective end-points to determine efficacy (almost all trials used a crossover design, included small numbers of patients and had limited statistical analysis of results), there is consistency in the data available that perhexiline is considerably more effective than placebo when used as monotherapy. Furthermore, it affords additional symptom relief in those already receiving maximal conventional anti-anginal therapy. However, there is a paucity of trials demonstrating the efficacy of low dosages of perhexiline (100 to 200 mg/day) in patients with refractory angina pectoris. Available evidence also suggests that the incidence of adverse events can be minimised, and the efficacy maintained, by keeping plasma perhexiline concentrations within a therapeutic range (150 to 600 micro g/L)

Mechanism of clozapine-induced agranulocytosis : current status of research and implications for drug development

Clozapine is an atypical antipsychotic agent that has several advantages over conventional antipsychotics, not least of which is its superior efficacy. However, the high risk of agranulocytosis (0.8% of patients) associated with clozapine therapy has resulted in restricted indications for its use.The mechanism of clozapine-induced agranulocytosis is not clear. The target cells affected are the myeloid precursors, although the mature neutrophil may also be targeted simultaneously. There is no convincing evidence of direct toxicity of the parent compound or its stable metabolites (demethyl-clozapine and clozapine N-oxide). Clozapine is also metabolised by liver microsomes, peripheral blood neutrophils and their bone marrow precursors to a chemically reactive intermediate that has been postulated to be a nitrenium ion. This toxic metabolite has been shown to covalently bind to neutrophil proteins, suggesting that it may be involved in the pathogenesis of the toxicity. However, it is not clear how toxicity is mediated. The nitrenium ion may bind to essential cellular proteins and disrupt neutrophil function or, alternatively, it may act as a hapten and initiate an immune reaction resulting in immune-mediated destruction of the neutrophil. Indirect evidence exists to support both mechanisms, although clear direct evidence is still lacking. The role of cytokines and apoptosis in the pathogenesis of the agranulocytosis is unclear.The reason why only approximately 1% of individuals who are treated with clozapine are affected by agranulocytosis has not been elucidated. Evidence exists to implicate both the major histocompatibility complex antigens and heat shock protein variants in determining individual susceptibility, although more patients of different ethnic backgrounds need to be studied.The ultimate aim of research into clozapine-induced agranulocytosis should be to either prospectively predict which individuals are going to develop agranulocytosis and/or to develop analogues that retain efficacy but are not toxic. The former is complicated by the fact that predisposition may be multifactorial, and thus prediction may require multiple tests that may be of statistical but not absolute validity. The latter depends on identifying the mechanism of toxicity and the chemical characteristics of clozapine that are responsible for the toxicity. This knowledge may allow rational design of new analogues that do not cause agranulocytosis.

Immunostaining for membrane attack complex of complement is related to cell necrosis in fulminant and acute hepatitis

BACKGROUND/AIMS

Complement activation is one of the mechanisms involved in inflammatory lesions. Initiation of the complement terminal pathway at a cell surface leads to the formation of a cytolytic membrane attack complex. Our study assess whether a membrane attack complex-associated mechanism is involved in liver cell necrosis of fulminant and subfulminant hepatitis.

METHODS

Immunostaining for membrane attack complex was compared with immunostaining for cytokeratin and complement inhibitory proteins such as membrane cofactor protein, decay-accelerating factor, and homologous restriction factor in 15 patients with fulminant hepatitis and 5 patients with nonfulminant acute hepatitis.

RESULTS

In all patients, hepatocytes surrounding necrotic areas, but not those at a distance, were stained for membrane attack complex, whereas the opposite staining pattern for membrane cofactor protein was observed. In controls, no hepatocyte staining for membrane attack complex was observed, whereas membrane cofactor protein, but not decay-accelerating factor or homologous restriction factor, was detected on hepatocytes.

CONCLUSIONS

Complement activation by antibody-dependent or non-antibody-dependent mechanisms might be involved in the pathogenesis of either fulminant or acute hepatitis. Modulation of membrane cofactor protein expression on hepatocytes might contribute to the sensitivity of hepatocytes to membrane attack complex and subsequent cell lysis.

The role of cytochrome P450 enzymes in hepatic and extrahepatic human drug toxicity

The human cytochrome P450 enzyme system metabolises a wide array of xenobiotics to pharmacologically inactive metabolites, and occasionally, to toxicologically active metabolites. Impairment of cytochrome P450 activity, which may be either genetic or environmental, may lead to toxicity caused by the parent compound itself. In practise, this usually only applies to drugs that have a narrow therapeutic index and when their clearance is critically dependent upon the fraction normally metabolised by that pathway. P450 enzymes may also convert the drug to a chemically reactive metabolite, which, if not detoxified, may lead to various forms of hepatic and extrahepatic toxicity, including cellular necrosis, hypersensitivity, teratogenicity, and carcinogenicity, depending on the site of formation and the relative stability of the metabolite, and the cellular macromolecule with which it reacts. Variation in the regulation and expression of the drug metabolising enzymes may play a key role in both interindividual variation in sensitivity to drug toxicity and tissue-specific damage. Avoidance of toxicity may be possible in rare instances by prediction of individual susceptibility or by designing new chemical entities that are metabolised by a range of enzymes (both cytochromes P450 and others) and do not undergo bioactivation.

Possible association between poor metabolism of mephenytoin and hepatotoxicity caused by Atrium, a fixed combination preparation containing phenobarbital, febarbamate and difebarbamate

Drug hepatotoxicity is partially determined by genetic factors involved in drug metabolism, which may involve the debrisoquine oxidation polymorphism mediated by cytochrome (CYP) 2D6. The purpose of this study was to assess the relationship between drug hepatotoxicity and another genetic polymorphism of drug oxidation, namely that of S-mephenytoin metabolism mediated by CYP2CMP. Mephenytoin hydroxylation capacity was assessed by a hydroxylation index in 24 patients with drug-induced hepatitis and in 23 healthy controls. Hydroxylation index was calculated as the ratio of S-mephenytoin dose to the (0-10 h) urinary excretion of 4-hydroxymephenytoin after oral administration of 100 mg racemic mephenytoin. The test was performed following the patient's recovery. In three patients, hepatitis was related to Atrium, a drug containing phenobarbital, febarbamate and difebarbamate. The mean hydroxylation index (+/- SD) value in patients with Atrium hepatitis (12.4 +/- 8.3) was markedly higher than that found in healthy controls (1.8 +/- 0.4) or in patients with other drug-induced hepatitis (2.5 +/- 3.3). Mean hydroxylation index values were similar in the two latter groups. Considered individually, oxidation capacity was low (hydroxylation index > 9) in two of the three patients with Atrium hepatitis and intermediate (hydroxylation index between 4 and 9) in the third patient. In contrast, all 23 healthy subjects exhibited a high oxidation capacity (hydroxylation index < 4). In the 21 patients with other drug-induced hepatitis, oxidation capacity was high in 19 subjects, intermediate in one subject with chlorpromazine hepatitis, and low in one subject with dapsone hepatitis.(ABSTRACT TRUNCATED AT 250 WORDS)

Fulminant hepatitis with severe lactate acidosis in HIV-infected patients on didanosine therapy

We report two cases of fulminant hepatic failure in HIV-1-infected patients treated with didanosine (ddI). Clinical manifestations including vomiting, diarrhoea and dyspnoea were identical in both cases. Biological data mainly revealed hepatic failure and lactic acidosis. Histological examination of liver biopsies showed diffuse microvesicular steatosis. The outcome was fatal in both patients. The only comparable case previously reported (Lai et al., 1991) showed close similarities in the clinical, biological and histological manifestations with microvesicular steatosis. This prompted us to suspect that ddI might be responsible for fulminant hepatitis in all three AIDS patients. This toxic effect may be added to the list of potential adverse events occurring during ddI therapy.

Idiosyncratic drug reactions: a mechanistic evaluation of risk factors

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The role of non-steroidal anti-inflammatory drugs in acute liver injury

OBJECTIVE

To investigate the association between use of non-steroidal anti-inflammatory drugs and serious, acute non-infectious liver injury.

DESIGN

Retrospective cohort study, cross over design.

SETTING

Health records from provincial database in Saskatchewan, Canada, 1982-6.

SUBJECTS

228,392 adults who contributed 645,456 person years. All were either using or had used non-steroidal anti-inflammatory drugs.

MAIN OUTCOME MEASURES

Number and type of prescriptions for non-steroidal anti-inflammatory drugs. Admission to hospital for newly diagnosed acute liver injury.

RESULTS

There were 34 admissions to hospital; 16 among subjects currently using non-steroidal anti-inflammatory drugs and 18 among subjects who were not. The incidence rate among current users was 9 per 100,000 person years (95% confidence interval 6 to 15 per 100,000 person years). Subjects currently using non-steroidal anti-inflammatory drugs had twice the risk of newly diagnosed liver injury as those not currently taking these drugs (rate ratio 2.3; 95% confidence interval 1.1 to 4.9) and an excess risk of 5 per 100,000 person years. The age and sex adjusted risk ratio was 1.7 (0.8 to 3.7). The strength of the association increased when only cases with no concomitant use of other hepatotoxic drugs were considered (4.0; 0.9 to 19.0). The rate ratio for people having received one to nine prescriptions was constant. There was no increased risk with long duration of treatment (1.0; 0.3 to 3.5).

CONCLUSIONS

There is a small excess risk of serious, acute non-infectious liver injury associated with the use of non-steroidal anti-inflammatory drugs.

Monitoring for adverse effects from systemic drugs used in dermatology

Systemic drugs with an associated element of risk are essential in managing many important dermatoses. This review identifies eight major drugs or drug groups used in dermatology that require systematic monitoring for adverse effects. The complete monitoring process is emphasized, including significant patient involvement in reporting key signs or symptoms that allow early diagnosis of many of these adverse effects. The concepts of "risk-risk" assessment and "critical toxicities" are defined, emphasizing their important role in maximizing drug benefits and safety. Drug-related risk factors, disease-specific risk factors, and patient characteristics or habits that increase the risks from systemic drugs are identified. Basic principles of monitoring for adverse effects, specific clinical features of the most important adverse effects, along with detailed monitoring guidelines for methotrexate, retinoids, dapsone, corticosteroids, and cyclosporine are presented.

Idiosyncratic reactions to antidepressants: a review of the possible mechanisms and predisposing factors

Antidepressants, a widely used group of drugs, are associated with a range of idiosyncratic reactions affecting in particular the liver, skin and both the hematological and central nervous systems. These reactions seem to be mediated by chemically reactive metabolites formed by the cytochrome P450 enzyme system, the toxicity occurring either directly or indirectly via an immune mechanism. Individual susceptibility is determined by factors, both genetic and environmental, which result in inadequate detoxication of the chemically reactive metabolite. Prevention of such reactions will depend on either the development of new compounds which are not converted to toxic metabolites or by prediction of individual susceptibility prior to drug administration.

Genetically determined oxidation polymorphism and drug hepatotoxicity. Study of 51 patients

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.