Drug metabolism in liver disease

Psychotropic drugs and liver disease: A critical review of pharmacokinetics and liver toxicity

The liver is the organ by which the majority of substances are metabolized, including psychotropic drugs. There are several pharmacokinetic changes in end-stage liver disease that can interfere with the metabolization of psychotropic drugs. This fact is particularly true in drugs with extensive first-pass metabolism, highly protein bound drugs and drugs depending on phase I hepatic metabolic reactions. Psychopharmacological agents are also associated with a risk of hepatotoxicity. The evidence is insufficient for definite conclusions regarding the prevalence and severity of psychiatric drug-induced liver injury. High-risk psychotropics are not advised when there is pre-existing liver disease, and after starting a psychotropic agent in a patient with hepatic impairment, frequent liver function/lesion monitoring is advised. The authors carefully review the pharmacokinetic disturbances induced by end-stage liver disease and the potential of psychopharmacological agents for liver toxicity.

Monitoring and managing hepatic disease in anaesthesia

Patients with liver disease have multisystem organ dysfunction that leads to physiological perturbations ranging from hyperbilirubinaemia of no clinical consequence to severe coagulopathy and metabolic disarray. Patient-specific risk factors, clinical scoring systems, and surgical procedures stratify perioperative risk for these patients. The anaesthetic management of patients with hepatic dysfunction involves consideration of impaired drug metabolism, hyperdynamic circulation, perioperative hypoxaemia, bleeding, thrombosis, and hepatic encephalopathy.

Impaired irinotecan biotransformation in hepatic microsomal fractions from patients with chronic liver disease

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

The anticancer agent irinotecan is a prodrug that is hydrolyzed by hepatic carboxylesterase to its active and toxic metabolite SN-38 and oxidized by CYP3A4 to its inactive metabolite APC. Irinotecan therapy is complicated by co-administered drugs that inhibit CYP3A4 and decrease APC formation and that indirectly increase SN-38 formation. Dose adjustment in cancer patients with liver disease has been recommended.

WHAT THIS STUDY ADDS

In microsomal fractions from patients with severe hepatic dysfunction both APC and SN-38 formation were decreased due to down-regulation of CYP3A4 and carboxylesterase enzymes. Thus relative SN-38 : APC formation was preserved. In some fractions the SN-38:APC ratio was increased, thus providing a possible explanation for clinical reports of increased SN-38 exposure in some patients with liver dysfunction. Close monitoring of SN-38 formation in patients with severe liver disease is warranted.

AIMS

Dose modification with the anticancer agent irinotecan is recommended in patients with severe liver dysfunction. This study evaluated the impact of liver disease on the relative formation of phase I products of irinotecan biotransformation in human microsomes in vitro.

METHODS

Microsomes from subjects with normal liver function and liver dysfunction (n=20) were assessed for irinotecan biotransformation and the expression of cytochrome P450 (CYP) 3A4 and carboxylesterase (CES) enzymes.

RESULTS

Liver disease down-regulated CYP3A4 expression (median 33% of control, range 0-126%, P<0.05) and impaired CYP3A4-dependent oxidation of irinotecan to the inactive 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]carbonyloxycamptothecin (APC) (median 0.2, range 0-1.21 pmol mg protein(-1) min(-1) compared with median 0.66, range 0-2.35 in control, P<0.01). CES-mediated hydrolysis of irinotecan to 7-ethyl-10-hydroxycamptothecin (SN-38) was also impaired in liver disease (median 8.38, range 0-20.7 pmol mg protein(-1) min(-1) compared with median 13.3, range 0-28.9 in control, P<0.05). In seven of 20 liver disease microsomes neither metabolite was detected but in three the SN-38:APC ratio was high (41-68) compared with the remaining 10 samples (ratio 11-36).

CONCLUSIONS

Down-regulation of CYP3A4 in liver disease decreased APC formation from irinotecan. SN-38 production was decreased and CES1 and 2 were down-regulated in most samples. However, in a subset of disease samples SN-38 production was relatively high because CYP3A4 activity was markedly impaired. This may account for clinical reports of increased SN-38 exposure in some patients with liver disease. Dose adjustments in cancer patients with liver disease who receive irinotecan are important and circulating SN-38 concentrations should be monitored closely.

A pilot study on the efficacy, pharmacokinetics and safety of atazanavir in patients with end-stage liver disease

OBJECTIVES

Antiretroviral combinations including atazanavir are currently not recommended in HIV-infected patients with end-stage liver disease (ESLD). The objective of our study was to evaluate efficacy, pharmacokinetics and safety of unboosted atazanavir in HIV-infected patients with ESLD screened for orthotopic liver transplantation (OLT(x)). Patients and methods Single-arm, 24 week pilot study. Atazanavir-naive patients undergoing highly active antiretroviral therapy were switched to atazanavir 400 mg/day plus two non-thymidine nucleoside reverse transcriptase inhibitors. Results Fifteen patients (10 males and 5 females) were included. In the study period, 2 patients were transplanted and 10 completed 24 weeks of atazanavir treatment. Median area under the concentration-time curve at week 4 was 19 211 ng.h/mL (IQR = 8959-27 500). At week 24, median atazanavir trough concentrations (C(trough)) per patient calculated across the study were above the minimum effective concentration (MEC = 100 ng/mL) in 8 of 10 subjects. Atazanavir C(trough) time-point values were always above the MEC in five patients. The other three subjects experienced only one determination below the MEC, with median atazanavir C(trough) levels across the study being above the MEC in two of them. At 8 of 11 time-points when atazanavir and proton pump inhibitors (PPIs) were co-administered and at 16 of 19 time-points in which patients had a concomitant tenofovir association, atazanavir C(trough) was above the MEC. Conclusions Unboosted atazanavir showed a favourable pharmacokinetic profile and was able to maintain or gain immuno-virological eligibility for OLT(x) in all patients. Limited biochemical toxicities (including unconjugated hyperbilirubinaemia) and allowance of concomitant administration of tenofovir and PPIs were observed.

Dental management of patients with end-stage liver disease

This article presents a review of end-stage chronic liver disease (cirrhosis) with emphasis on the clinical presentation, diagnosis, and complications of cirrhosis, along with their medical and surgical management and prognosis. This article also discusses the evaluation and management of the dental patients with cirrhosis, including the implications decreased hepatic function has on drugs commonly used in dental treatment.

An overview of psychiatric issues in liver disease for the consultation-liaison psychiatrist

Liver disease is a common cause of morbidity and mortality in the United States and elsewhere. Arising from infectious, hereditary, or toxin-induced sources, the detection of liver disease often requires a high index of suspicion. Clinical presentations are highly variable and are often accompanied by neuropsychiatric symptoms. This fact, along with an increased incidence of liver disease among patients with primary psychiatric disorders and the presence of varied drug use, complicates the tasks of providing care to patients with liver disease. To assist the consultation-liaison psychiatrist, the authors present the first of a two-part series focused on psychiatric issues in liver disease.

The Effects of Liver and Renal Dysfunction on the Pharmacokinetics of Sedatives and Analgesics in the Critically Ill Patient

In critically ill patients, the duration of effect and dose-response relationship of sedative and analgesic drugs can be significantly affected by the presence of renal or hepatic dysfunction. Alterations in pharmacokinetics and pharmacodynamics vary according to the degree of organ impairment and presence of comorbid illnesses. This article reviews the principals that govern the absorption, distribution, metabolism, and elimination of sedatives and analgesics during renal and hepatic impairment. By anticipating changes in pharmacokinetics, and by routinely assessing the clinical response to therapy, unintended adverse consequences of sedative and analgesic drug therapy may be avoided.

Antiretroviral drug pharmacokinetics in hepatitis with hepatic dysfunction

Chronic viral hepatitis is common among persons with HIV-1 infection, because of shared modes of transmission, and coinfection results in accelerated liver damage, compared with persons with chronic viral hepatitis alone. The use of highly active antiretroviral therapy (HAART) has led to a significant decrease in the morbidity and mortality associated with HIV-1 infection. A number of the medications that are commonly used in HAART regimens are metabolized by the hepatic CYP enzymes, which raises the possibility of significant interactions between antiretroviral medications and hepatic impairment induced by chronic viral hepatitis. Although the data are still very scant, the pharmacokinetics of several antiretroviral medications have been shown to be significantly altered in the presence of liver disease. In the present report, we review the available data and consider potential options, such as dose adjustment and therapeutic drug monitoring, for the administration of antiretroviral therapy to patients with significant hepatic impairment.

Comparison of MEGX (monoethylglycinexylidide) and antipyrine tests in patients with liver cirrhosis

The aim of the study was to compare the feasibility of the MEGX (monoethylglycinexylidide) and antipyrine tests in reference to standard biochemical parameters used for liver assessment in cirrhotic patients. The study was carried out in 44 subjects: 14 healthy controls and 30 cirrhotic patients classified according to the Child-Pugh's score to subgroups A (n=11), B (n=12) and C (n=7). All subjects underwent two dynamic liver tests, i.e. MEGX (monoethylglycinexylidide) and antipyrine test in a crossover schedule with at least 5-day interval. For the MEGX, lidocaine was administrated intravenously, at a dose of 1 mg/kg, and blood samples for MEGX assay were collected after 15 minutes. MEGX concentrations were measured by fluorescence polarization immunoassay. The antipyrine concentrations were evaluated following a single oral administration of 1000 mg antipyrine. The blood was sampled for 24 hours after the drug administration, and antipyrine concentrations were measured spectrophotometrically. Standard biochemical parameters used for liver assessment were measured by means of routine laboratory methods. It was concluded that in patients liver with cirrhosis, liver dynamic tests were better predictors of hepatic function. The MEGX test was more feasible in clinical setting, but it was noted that antipyrine test was more sensitive in staging liver cirrhosis.

Hazard characterisation of chemicals in food and diet. dose response, mechanisms and extrapolation issues

Hazard characterisation of low molecular weight chemicals in food and diet generally use a no-observed-adverse-effect level (NOAEL) or a benchmark dose as the starting point. For hazards that are considered not to have thresholds for their mode of action, low-dose extrapolation and other modelling approaches may be applied. The default position is that rodents are good models for humans. However, some chemicals cause species-specific toxicity syndromes. Information on quantitative species differences is used to modify the default uncertainty factors applied to extrapolate from experimental animals to humans. A central theme for extrapolation is unravelling the mode of action for the critical effects observed. Food can be considered as an extremely complex and variable chemical mixture. Interactions among low molecular weight chemicals are expected to be rare given that the exposure levels generally are far below their NOAELs. Hazard characterisation of micronutrients must consider that adverse effects may arise from intakes that are too low (deficiency) as well as too high (toxicity). Interactions between different nutrients may complicate such hazard characterisations. The principle of substantial equivalence can be applied to guide the hazard identification and hazard characterisation of macronutrients and whole foods. Macronutrients and whole foods must be evaluated on a case-by-case basis and cannot follow a routine assessment protocol.

Activities of Cytochrome P450 Enzymes in Liver and Kidney Microsomes from Systemic Carnitine Deficiency Mice with a Gene Mutation of Carnitine/Organic Cation Transporter

Juvenile visceral steatosis (jvs) mice, isolated from the C3H-H-2 degrees strain, exibit a systemic carnitine deficiency (SCD) phenotype and develop fatty liver, hyperammonemia and hypoglycemia. This phenotype is caused by a missense mutation (Leu352Arg) of a sodium-dependent carnitine/organic cation transporter, Octn2 (Slc22a5). The jvs mouse could be a useful model for pharmacokinetics and drug metabolism studies concerning Octn2 substrate drugs. In the present study, the effects of the SCD phenotype on the cytochrome P450 (P450 or CYP) dependent activities of four endobiotic and seven xenobiotic oxidations catalyzed by liver and kidney microsomes from jvs mice were investigated. The jvs-type mutation was genotyped by PCR-RFLP. The contents of total P450 and NADPH-P450 reductase were similar in the the liver microsomes from male or female mice of the wild-type and those heterozygous or homozygous for the jvs-type mutation. The 6beta-hydroxylation activities of testosterone and progesterone (marker for Cyp3a) based on the protein contents were 1.2- to 2.0-fold higher in liver microsomes from jvs/jvs-type mice compared to jvs/wt- or wt/wt-type mice. Coumarin 7-hydroxylation activities (marker for Cyp2a) were decreased to 0.7-fold in the male jvs/jvs-type mice. The activities of lauric acid 12-hydroxylation (a marker for Cyp4a) and aniline p-hydroxylation (a marker for Cyp2e1) in liver microsomes were increased 1.4- to 1.9-fold in female jvs/jvs-type mice. Genotoxic activation of 2-aminofluorene (a marker for Cyp4b1) by male and female mouse kidney microsomes were not affected by the SCD phenotype. These results demonstrated that the SCD phenotype affected the P450-dependent catalytic activities in liver microsomes. The jvs mouse could provide valuable information in drug interaction and drug metabolism studies of OCTN2 substrate drugs and new compounds in development.

Pharmacokinetics of sabeluzole and dextromethorphan oxidation capacity in patients with severe hepatic dysfunction and healthy volunteers

AIMS

The primary objective of this study was to determine how the pharmacokinetics of sabeluzole, an investigational drug with specific effects on memory and learning abilities, are affected by chronic liver disease. Since sabeluzole is metabolised by CYP2D6, a secondary objective was to study the correlation between CYP2D6 activity (as assessed by the dextromethorphan dextrorphan metabolic ratio) and hepatic dysfunction.

METHODS

The single-dose pharmacokinetics of sabeluzole (10 mg) was compared in 10 healthy Caucasian subjects and 10 patients with severe hepatic dysfunction. The urinary dextromethorphan/dextrorphan (DMP/DRP) metabolic ratio was determined after intake of 20 mg dextromethorphan (NODEX capsules).

RESULTS

The terminal half-life of sabeluzole was significantly prolonged in subjects with severe hepatic dysfunction vs healthy subjects (respectively 39.3 +/- 11.5 h; 17.5 +/- 10.2 h (mean +/- s.d.)). The areas under the curve (AUC) were significantly higher in subjects with severe hepatic dysfunction than in healthy volunteers (681 +/- 200 ng ml(-1) h vs 331 +/- 282 ng ml(-1) h). There was a significant correlation between the AUC(0,infinity) and the DMP/DRP metabolic ratio in healthy volunteers and subjects with severe hepatic dysfunction. AUC was greater and elimination of sabeluzole slower in poor metabolizers compared with extensive metabolizers.

CONCLUSIONS

These results suggest that a) sabeluzole dose should be reduced in patients with severe hepatic dysfunction and b) the AUC of sabeluzole is linked to individual CYP2D6 activity.

Effects of liver disease on pharmacokinetics. An update

Liver disease can modify the kinetics of drugs biotransformed by the liver. This review updates recent developments in this field, with particular emphasis on cytochrome P450 (CYP). CYP is a rapidly expanding area in clinical pharmacology. The information currently available on specific isoforms involved in drug metabolism has increased tremendously over the latest years, but knowledge remains incomplete. Studies on the effects of liver disease on specific isoenzymes of CYP have shown that some isoforms are more susceptible than others to liver disease. A detailed knowledge of the particular isoenzyme involved in the metabolism of a drug and the impact of liver disease on that enzyme can provide a rational basis for dosage adjustment in patients with hepatic impairment. The capacity of the liver to metabolise drugs depends on hepatic blood flow and liver enzyme activity, both of which can be affected by liver disease. In addition, liver failure can influence the binding of a drug to plasma proteins. These changes can occur alone or in combination; when they coexist their effect on drug kinetics is synergistic, not simply additive. The kinetics of drugs with a low hepatic extraction are sensitive to hepatic failure rather than to liver blood flow changes, but drugs having a significant first-pass effect are sensitive to alterations in hepatic blood flow. The drugs examined in this review are: cardiovascular agents (angiotensin converting enzyme inhibitors, angiotensin II receptor antagonists, calcium antagonists, ketanserin, antiarrhythmics and hypolipidaemics), diuretics (torasemide), psychoactive and anticonvulsant agents (benzodiazepines, flumazenil, antidepressants and tiagabine), antiemetics (metoclopramide and serotonin antagonists), antiulcers (acid pump inhibitors), anti-infectives and antiretroviral agents (grepafloxacin, ornidazole, pefloxacin, stavudine and zidovudine), immunosuppressants (cyclosporin and tacrolimus), naltrexone, tolcapone and toremifene. According to the available data, the kinetics of many drugs are altered by liver disease to an extent that requires dosage adjustment; the problem is to quantify the required changes. Obviously, this requires the evaluation of the degree of hepatic impairment. At present there is no satisfactory test that gives a quantitative measure of liver function and its impairment. A critical evaluation of these methods is provided. Guidelines providing a rational basis for dosage adjustment are illustrated. Finally, it is important to consider that liver disease not only affects pharmacokinetics but also pharmacodynamics. This review also examines drugs with altered pharmacodynamics.

Effect of hepatic insufficiency on pharmacokinetics and drug dosing

The liver plays a central role in the pharmacokinetics of many drugs. Liver dysfunction may not only reduce the plasma clearance of a number of drugs eliminated by biotransformation and/or biliary excretion, but it can also affect plasma protein binding which in turn could influence the processes of distribution and elimination. In addition, reduced liver blood flow in patients with chronic liver disease will decrease the systemic clearance of flow limited (high extraction) drugs and portal-systemic shunting may substantially reduce their presystemic elimination (first-pass effect) following oral administration. When selecting a drug and its dosage regimen for a patient with liver disease additional considerations such as altered pharmacodynamics and impaired renal excretion (hepatorenal syndrome) of drugs and metabolites should also be taken into account. Consequently, dosage reduction is necessary for many drugs administered to patients with chronic liver disease such as liver cirrhosis.

Selective effect of liver disease on the activities of specific metabolizing enzymes: investigation of cytochromes P450 2C19 and 2D6

BACKGROUND AND OBJECTIVES

Drug metabolism is influenced by liver disease because of the central role that the liver plays in metabolic activities in the body. However, it is still unclear how activities of specific drug-metabolizing enzymes are influenced by the presence and severity of liver disease. As a consequence, alteration in metabolism of specific drugs cannot be easily predicted or appropriate dosage adjustment recommendations made.

METHODS

The activities of cytochromes P450 (CYP) 2C19 and 2D6 were investigated in a group of patients with mild or moderate liver disease (n = 18) and a group of healthy control subjects (n = 10). The disposition of racemic mephenytoin for CYP2C19 and debrisoquin for CYP2D6 were characterized in plasma and urine samples collected over 192 hours.

RESULTS

The elimination of S-mephenytoin was severely reduced among patients with liver disease, resulting in a 79% decrease in plasma clearance for all patients combined. This reduction was related to the severity of disease, patients with moderate disease being affected more severely than patients with mild disease. Similar differences were observed in the urinary excretion of 4'-hydroxymephenytoin metabolite. By contrast, there was no effect on the disposition of R-mephenytoin or debrisoquin.

CONCLUSION

These results show selectivity in the effect of liver disease on activities of specific metabolizing enzymes, CYP2C19 being more sensitive than CYP2D6. They suggest that recommendations for modification in drug dosage in the presence of liver disease should be based on knowledge of the particular enzyme involved in metabolism of the drug. The results emphasize the need for further studies of each specific drug-metabolizing enzyme in the presence of liver disease.

Clinical importance of non-genetic and genetic cytochrome P450 function tests in liver disease

Liver disease is associated with reduced metabolic capacity for drugs that are metabolized by oxidative biotransformation. Three cytochrome P450 (P450 or CYP) gene families in liver microsomes (CYP 1, CYP2 and CYP3) appear to be responsible for much of the drug metabolism that takes place. The genetic polymorphism of the CYPs responsible for debrisoquine/ sparteine (CYP2D6) metabolism and S-mephenytoin (CYP2C19) metabolism has been well documented, but information on the impairment of each isoform in liver disease is still limited. There are two types of hepatic P450 function tests. One type consists of non-genetic P450 function tests (CYP1A2, 2A6, 2C9/10, 2E1 and 3A3/4), and probe drugs include caffeine, catalysed by CYP1A2, coumarin by CYP2A6, phenytoin by CYP2C6, chlorzoxazone by CYP2E1, and nifedipine, erythromycin and lidocaine by CYP3A3/4. The second type of genetic P450 function tests (CYP2C19 and CYP2D6) involves probe drugs such as S-mephenytoin, catalysed by CYP2C19, and debrisoquine and sparteine, catalysed by CYP2D6. The metabolism of the probe drugs used in non-genetic P450 function tests in patients with liver disease falls into two categories: reduced (CYP1A2, CYP2C, 2E1 and 3A) and unchanged (CYP2C). In genetic P450 function tests there seems to be a lesser degree of inhibition in poor metabolizers (PMs) than extensive metabolizers (EMs) among patients with liver disease. There have been very few reports on changes in metabolism of the probe drugs used in genetic P450 function tests in liver disease. In this paper the subject is reviewed.

Liver metabolism of porphyrins and haem

The liver is an active site for the biosynthesis of haem and porphyrinogens/porphyrins, which are intermediates of the haem biosynthetic pathway, because haem is required for functional activity of the cytochrome P 450 system and other critical hepatic haemoproteins. The production of hepatic haem is regulated primarily through the activity of aminolaevulinic acid synthase which is the first and normally rate-limiting enzyme of the pathway. This is, in turn, controlled by a putative regulatory haem pool. Hepatic haem can be repleted by the intravenous administration of haem, which is the basis for haem therapy in patients with acute porphyric attacks. The liver catabolizes haem to bilirubin through microsomal haem oxygenase activity and excretes haem into bile along with porphyrins. Biliary excretion of porphyrins increases significantly in patients with some types of porphyria. In protoporphyria this may cause liver damage as a result of protoporphyrin toxicity. The delineation of the pathway for protoporphyrin excretion into bile should facilitate therapy in protoporphyria by identifying ways in which protoporphyrin excretion can be enhanced.

Pharmacokinetics of ethanol in patients with renal failure before and after hemodialysis

We studied the pharmacokinetics of ethanol in seven patients suffering from terminal renal failure before and after they underwent hemodialysis. Ethanol (0.40 g/kg) was administered in the morning after an overnight fast by a constant rate intravenous (i.v.) infusion over 45 min. After removing a mean fluid volume of 2.46 +/- 0.48 liters (+/- SD), span 1.76-3.43 liters by hemodialysis, the same subjects received a second i.v. infusion of ethanol after they had eaten lunch. At exactly timed intervals of 0, 45, 90, 105, 120, 135, 150, 165, and 180 min from the start of the infusion, two blood-samples were drawn and the plasma portion of one of them was obtained by centrifugation. The concentration of ethanol in blood and plasma was determined by headspace gas chromatography and the water-content of whole blood was determined from the change in weight after desiccation. Plasma always contained a higher concentration of ethanol than whole blood and the mean plasma/whole blood ratio in patients with renal failure was 1.07:1 (span 1.05-1.10). The rate of ethanol disappearance from blood (beta-slope) was faster (0.185 +/- 0.013 versus 0.157 +/- 0.022 g/l/h), the Co value was higher (0.79 +/- 0.08 versus 0.73 +/- 0.10 g/l) and the apparent volume of distribution (Vd) of ethanol was lower (0.507 +/- 0.049 versus 0.558 +/- 0.078 l/kg) after hemodialysis. The water content of whole blood was significantly higher (P < 0.001) before dialysis (88.6 +/- 1.97 g/100 ml) compared with after dialysis (87.4 +/- 2.01 g/100 ml). The higher Vd for ethanol and lower Co as well as higher blood-water content are to be expected for a over hydrated condition before hemodialysis. The swifter rate of ethanol elimination from blood (beta-slope) after hemodialysis should be interpreted with caution because eating a meal before the second infusion of ethanol is a confounding factor. Nevertheless, the rate of elimination of ethanol from blood in patients with renal failure agreed reasonably well with values expected for healthy subjects, namely mean 0.15 g/l/h spanning from 0.10 to 0.20 g/l/h.

Impairment of the metabolism of dipyrone in asymptomatic carriers of the hepatitis B virus

BACKGROUND

The pharmacokinetics of a number of drugs has been shown to be impaired in patients with acute or chronic viral liver disease.

OBJECTIVE

To examine the effect of the asymptomatic hepatitis B virus carrier state on the metabolism of dipyrone (INN, metamizole) as a model drug.

METHODS

The pharmacokinetics of the metabolites of dipyrone-4-methylaminoantipyrine, 4-aminoantipyrine, 4-formylaminoantipyrine, and 4-acetylaminoantipyrine-after a 1.0 gm oral dose of dipyrone were evaluated in nine asymptomatic carriers of hepatitis B virus with normal liver function tests and nine healthy subjects. All subjects displayed the slow acetylator phenotype.

RESULTS

The nonrenal (metabolic) clearance of 4-methylaminoantipyrine was significantly reduced (mean +/- SEM) (123.3 +/- 15.8 versus 182.9 +/- 15.1 ml.min-1, respectively; p < 0.02) in the carriers of hepatitis B virus compared with the healthy subjects, and the elimination half-life of this metabolite was significantly longer (3.69 +/- 0.35 versus 2.64 +/- 0.28 hours, respectively; p < 0.03). The formation clearances of 4-aminoantipyrine and 4-formylaminoantipyrine were significantly smaller in the carriers of hepatitis B virus compared with healthy subjects (33.8 +/- 6.2 versus 55.2 +/- 6.4 ml.min-1; p < 0.03, and 16.7 +/- 2.2 versus 34.2 +/- 4.2 ml.min-1; p < 0.002; respectively). However, the elimination half-life of 4-formylaminoantipyrine was found to be slightly shorter in the carriers of hepatitis B virus. No significant differences were noted between the groups in the pharmacokinetics of 4-acetylaminoantipyrine.

CONCLUSION

The metabolism of dipyrone is impaired in asymptomatic carriers of hepatitis B virus. Clinically latent infection with hepatitis B virus seems to exert a differential effect on metabolism of the drug. Oxidative pathways to produce 4-aminoantipyrine and 4-formylaminoantipyrine were significantly affected, whereas acetylation remained intact. This study provided an additional example of the effect of a virus on the disposition of a drug.

The effect of experimental fascioliasis on the pharmacokinetics of antipyrine and sulphadimidine in desert sheep

Healthy adult male desert sheep were experimentally infected with Fasciola gigantica, to investigate the influence of experimental fasciolasis on the pharmacokinetics of antipyrine and sulphadimidine. Each animal received 500 metacercariae orally. The experimental infection was confirmed histologically, by detection of Fasciola eggs in faeces and by measuring the activities of the enzymes sorbitol dehydrogenase (SD), glutamate dehydrogenase (GD) and aspartate aminotransferase (AST) in plasma during the course of the disease. Changes in the pharmacokinetics of antipyrine and sulphadimidine were reported in the experimentally infected animals. Significant prolongation of antipyrine half life was observed 16 weeks after infection. The half-life of sulphadimidine was also significantly prolonged 5, 9 and 16 weeks after infection. Clearance of the sulphonamide was decreased significantly 5 and 9 weeks after infection and it regained its pre-infection value 16 weeks after infection.

Medical considerations for dental care of patients with alcohol-related liver disease

More than 7 percent of all adults in the United States have met diagnostic criteria for alcohol abuse and alcohol dependence. Many of these people and even occasional users of alcohol may exhibit medical complexities, particularly liver disease, that can adversely affect provision of routine dental care. This article highlights some of the important clinical topics associated with alcoholic liver disease as it relates to dental care and provides guidelines on treatment of affected people.

Trimethadione as a probe drug to estimate hepatic oxidizing capacity in humans

Trimethadione (TMO) has the properties required of probe drugs for the evaluation of hepatic drug-oxidizing capacity in humans in vivo. TMO is demethylated to dimethadione (DMO), its only metabolite, in the liver after oral administration. Involvement of two cytochrome P450's--CYP2C9 and 3A4--in TMO metabolism has been seen in humans, but involvement of 1A2 is not clearly established. In humans with various types of liver disease and hepatectomy, the serum DMO/TMO ratios, which were measured on blood samples obtained by a single collection 4 hr after oral administration of TMO, correlated well with the degree of hepatic damage. This finding suggests that TMO may be used as a probe drug in the rapid determination of the functional reserve mass of the liver as well as hepatic drug-oxidizing capacity in humans in vivo.

Drug metabolism in liver disease: implications for therapeutic drug monitoring

Over the last decades, a bulk of evidence has accumulated on the effect of liver disease on drug metabolism. It has convincingly been demonstrated that liver disease is associated with a reduced metabolic capacity with respect to drugs undergoing oxidative biotransformation, whereas conjugation reactions, especially glucuronidation, seem less affected. Nevertheless, many data have been conflicting, and it has become increasingly clear that differences in patient selection and severity of disease can account for these. Further, more recent communications suggest that liver disease led to a differential alteration of the cytochrome P-450s with regard to protein content and activity. From a clinical point of view, these findings may have important implications. However, when treating liver patients, we still have no generally accepted model for dose predictions; the best approach should be empiric and based on the clinical response. In selected cases, monitoring of plasma drug concentrations and liver function is recommended.

Dipyrone metabolism in liver disease

BACKGROUND AND OBJECTIVES

Dipyrone is an analgesic, antipyretic, and anti-inflammatory drug. After oral administration it is hydrolyzed to 4-methylaminoantipyrine and further metabolized to 4-aminoantipyrine, 4-formylaminoantipyrine, and 4-acetylaminoantipyrine. This study investigated the disposition of dipyrone metabolites in 12 hospitalized patients with cirrhosis (age, 25 to 65 years) and 27 healthy subjects of two age groups (young, 21 to 40 years; elderly, 73 to 90 years).

METHODS

Subjects received 1 gm dipyrone orally, and blood samples were drawn and urine collected over 72 hours. Plasma and urine concentrations of the four metabolites were determined by HPLC.

RESULTS

4-Methylaminoantipyrine terminal elimination half-life (t1/2 beta) in patients with cirrhosis was prolonged compared with young and elderly subjects (mean +/- SEM, 10.6 +/- 0.6 versus 3.1 +/- 0.2 and 4.9 +/- 0.6 hours, p < 0.001), and the nonrenal clearance was reduced compared with the young subjects (1.069 +/- 0.243 versus 2.165 +/- 0.154 ml/min/kg, p < 0.005). 4-Formylaminoantipyrine was undetectable in two patients and in the remaining 10 patients, t1/2 was longer than in the young subjects (26.4 +/- 4.3 versus 10.8 +/- 0.7 hour, p < 0.01), whereas the elderly had intermediate values (18.1 +/- 2.8 hours). Clearance for production of 4-formylaminoantipyrine was reduced in the patients with cirrhosis than in the young and elderly subjects (0.109 +/- 0.024 versus 0.363 +/- 0.031 and 0.340 +/- 0.053 ml/min/kg, p < 0.001). The acetylation phenotype was determined to evaluate the pharmacokinetic parameters of 4-aminoantipyrine and 4-acetylaminoantipyrine. Prolongation of the 4-aminoantipyrine t1/2 and decrease in its clearance for production was found for the patients with cirrhosis, both slow and rapid acetylators, compared with the young and elderly subjects (p < 0.01). 4-Acetylaminoantipyrine t1/2 was also prolonged for patients with cirrhosis, slow and rapid acetylators, compared with the young subjects (p < 0.005). In the slow acetylators, clearance for production of 4-acetylaminoantipyrine did not differ between the patients with cirrhosis and the young subjects (p < 0.5); however, a difference was found for the rapid acetylators (p < 0.001).

CONCLUSION

Our results show that the disposition of 4-methylaminoantipyrine, 4-aminoantipyrine, 4-formylaminoantipyrine, and 4-acetylaminoantipyrine is reduced by chronic liver disease after a single oral dose of dipyrone.

Assessment of liver metabolic function. Clinical implications

Inter- and intraindividual variability in pharmacokinetics of most drugs is largely determined by variable liver function as described by parameters of hepatic blood flow and metabolic capacity. These parameters may be altered as a result of disease affecting the liver, genetic differences in metabolising enzymes, and various types of drug interactions, including enzyme induction, enzyme inhibition or down-regulation. With the now known large number of drug metabolising enzymes, their differential substrate specificity, and their differential induction or inhibition, each test substance of liver function should be used as a probe for its specific metabolising enzyme. Thus, the concept of model test-substances providing general information about liver function has severe limitations. To test the metabolic activity of several enzymes, either several test substances may be given (cocktail approach) or several metabolites of a single test substance may be analysed (metabolic fingerprint approach). The enzyme-specific analysis of liver function results in a preference for analysis of the metabolites rather than analysis of the clearance of the parent test substance. There are specific methods to quantify the activity of cytochrome P450 enzymes such as CYP1A2, CYP2C9, CYP2C19MEPH, CYP2D6, CYP2E1, and CYP3A, and phase II enzymes, such as glutathione S-transferases, glucuronyl-transferases or N-acetyltransferases, in vivo. Interactions based on competitive or noncompetitive inhibition should be analysed specifically for the cytochrome P450 enzyme involved. At least 5 different types of cytochrome P450 enzyme induction may result in major variability of hepatic function; this may be quantified by biochemical parameters, clearance methods, or highly enzyme-specific methods such as Western blot analysis or molecular biological techniques such as mRNA quantification in blood and tissues. Therapeutic drug monitoring is already implicitly used for quantification of the enzyme activities relevant for a specific drug. Selective impairment of hepatic enzymes due to gene mutations may have an effect on the pharmacokinetics of certain drugs similar to that caused by cirrhosis. Assessment of this heritable source of variability in liver function is possible by in vivo or ex vivo enzymological methods. For genetically polymorphic enzymes and carrier proteins involved in drug disposition, molecular genetic methods using a patient's blood sample may be used for classification of the individual into: (i) the impaired or poor metaboliser (homozygous deficient); (ii) the extensive (homozygous active) metaboliser group; and (iii) the moderately extensive metaboliser (heterozygous) group. For hepatic blood flow determinations, galactose or sorbitol given at relatively low doses may be much better indicators than the indocyanine green.(ABSTRACT TRUNCATED AT 400 WORDS)

Pharmacokinetics of zidovudine in HIV-positive patients with liver disease

The pharmacokinetics of zidovudine (ZDV) have been studied in eight AIDS patients with normal liver function, and in four AIDS patients with liver disease. Patients who were previously untreated with ZDV were given 250 mg ZDV, and plasma levels of ZDV and its glucuronic metabolite, GZDV, were determined at 0.5, 1, 1.5, 2, 3, and 4 hours after the dose. In patients with liver disease, Cmax and AUC of ZDV were higher, the oral clearance was only one-eighth that of patients without liver disease, and the elimination half-life was longer. There was a trend for concentrations of the principal metabolite, GZDV, to be lower in patients, and, therefore, the ratio of the AUC for GZDV to that for ZDV was much lower in patients with liver disease. Therefore, HIV-seropositive patients with liver disease had the same markedly altered disposition of ZDV as seronegative patients with liver disease. Although this therapy was not clearly associated with a higher incidence of toxicity, some patients with liver disease had to discontinue therapy because of intolerance; therefore, plasma levels of these patients should be monitored when such therapy is undertaken.

Alterations of hepatic drug metabolism in mice following infection with the murine retrovirus LP-BM5

Infection of mice with the murine retrovirus mixture LP-BM5 caused a retroviral infection with many similarities to human HIV infection. We have reported alterations in hepatic drug metabolism which progressed during the course of this infection. Hexobarbital-induced sleep time increased 1.5-2.2-fold above uninfected controls after 10 to 19 weeks post infection. Inhibition of spectral cytochrome P-450 levels by 25 to 30% was observed between 15 and 17 weeks post-infection, and there were changes in specific microsomal enzyme activities. The microsomal cocaine demethylase activity was reduced by 40%, whereas cytosolic enzyme activities were increased by 1.5-2.0-fold. These alterations may contribute to the altered metabolism of drugs of abuse reported in MAIDS mice. The mechanism for these alterations is not known, although the effects correspond temporally to reported infiltration of the liver with immunoblasts and plasma cells. This suggests a role for the immune system or for mediators released by cells of the immune system which could account for these observations. An understanding of the effects of infection on drug metabolism is important because of their impact on the efficacy and safety of drugs for use in AIDS patients).

Pharmacokinetics of naftopidil, a novel anti-hypertensive drug, in patients with hepatic dysfunction

The pharmacokinetics of naftopidil, a novel alpha-1 adrenoceptor-blocking antihypertensive, were investigated in ten patients (9M/1F) with hepatic dysfunction after oral administration (50 mg, tablet) and after an intravenous infusion of 5.0 mg over 2 minutes. Results were compared to a control group of 12 healthy subjects (6M/6F) of a previous investigation, which was carried out according to the identical study protocol. The pharmacokinetic parameters obtained for the i.v. administration were comparable in both groups (half life 3.6 +/- 3.4 hours in liver-impaired subjects versus 3.3 +/- 2.1 hours in controls; clearance 11.9 +/- 4.7 ml/minute/kg versus 11.0 +/- 1.6 ml/minute/kg). Following oral administration the plasma levels and half-life times of naftopidil were significantly increased in liver impairment (t1/2 16.6 +/- 19.3 hours versus 5.4 +/- 3.2 hours in controls; P = 0.012). Mean values for the absolute bioavailability in patients with hepatic dysfunction were significantly higher (mean 75%, median 53%, range 13.4-211.0%) compared to healthy subjects (mean 17%, median 16%, range 6.7-29.6%, P = 0.001). Reduction of functional hepatic blood flow in chronic liver disease or, as evidenced in one case as a consequence of shunt surgery, is the probable cause of the observed alteration in naftopidil kinetics. This phenomenon occurred only following the oral 50 mg dose whereas the intravenous 5 mg dose obviously still could be normally handled. Naftopidil demethylation and hydroxylation were both less and non-uniformly affected. The pharmacokinetic findings suggest that in patients with severe hepatic impairment or evidence for marked changes in hepatic blood flow the dose of naftopidil may require adjustment to the lower end of the therapeutic range and/or may be limited to once daily. However, before definite conclusions can be drawn, further steady-state studies are required. Despite the pharmacokinetic discrepancies no difference in drug tolerability was seen between patients and healthy subjects.

Variables affecting nicotine metabolism

Nicotine metabolism is exceedingly sensitive to perturbation by numerous host factors. To reduce the large variations and discrepancies in the literature pertaining to nicotine metabolism, investigators in future studies need to recognize and better control these host factors. Recent advances in the understanding of nicotine metabolism have suggested new approaches to elucidating underlying mechanisms of certain toxic effects associated with cigarette smoking.

Factors and conditions affecting the glucuronidation of oxazepam

The aim of the present work was to investigate the impact of disease states and environmental and host factors on the glucuronidation of oxazepam. Glucuronidation represents quantitatively one of the most important metabolic conjugation pathways (phase II) in man for the inactivation and detoxication of xenobiotics and endogenous compounds and the liver is the major site for it to take place. Far less attention has been paid to the conjugation reactions in previous clinical research in this field compared to the immense interest in the oxidative biotransformation pathways (phase I). This fact is mainly due to the latter giving rise to active or reactive metabolites with a toxicological potential. The metabolism of oxazepam expresses exclusively the capacity for glucuronide formation. It was a prerequisite to establish the bioavailability of oxazepam prior to succeeding studies on the oral disposition of the drug. A preparation for intravenous administration was created. Clearance was chosen as measurement of the capacity to glucuronidate oxazepam. Severe decompensated liver disease was associated with a significant decrease in oxazepam clearance, that became even more obvious when corrected for by a diminished binding to plasma proteins. This increase in free fraction of oxazepam was substantial and could mainly be accounted for by low plasma albumin values. The results are in part a settlement with earlier studies on glucuronidation in liver disease and they may undoubtedly be ascribed to the severe degree of liver disease. For the first time it was shown that hypothyroidism led to a decline in the clearance and metabolism of oxazepam and paracetamol that is mainly biotransformed by glucuronidation. It was concluded that the enzymes responsible for glucuronidation in hypothyroidism are under the influence of thyroid hormones as is the case with oxidative enzymes. Further studies focused on the effect of host and environmental factors on glucuronidation. A commercially available very low calorie product for the treatment of obesity resulted in a decrease in oxazepam clearance and a lack of co-factors as a consequence of the low calorie intake was explanatorily proposed. Beta-adrenoceptor antagonists are often prescribed together with other drugs and close knowledge on interactions is mandatory but insufficient in regard of drugs being glucuronidated. Despite the mutual metabolic pathway labetalol exerted no dispositional alterations concerning oxazepam. It was moreover suggested that very elderly subjects between the age of 80 to 94 years had a reduced clearance of oxazepam.(ABSTRACT TRUNCATED AT 400 WORDS)

Psychopharmacologic issues in organ transplantation. Part I: Pharmacokinetics in organ failure and psychiatric aspects of immunosuppressants and anti-infectious agents

This article discusses pharmacokinetics and pharmacodynamics during hepatic, renal, and cardiovascular insufficiencies. Hepatic metabolism of psychotropic drugs and of drugs commonly used in transplant patients that have neuropsychiatric side effects is discussed. Neuropsychiatric effects of immunosuppressant agents, including cyclosporine, corticosteroids, azathioprine, OKT3, and FK 506, are reviewed. Certain infections occur more often in immunosuppressed patients; their treatment with antiviral, antifungal, and antibiotic drugs may have neuropsychiatric consequences. Because of altered drug sensitivities and metabolism, drug interactions, and severe medical illness, most drugs are used in reduced doses.

The pharmacokinetics of intravenous ondansetron in patients with hepatic impairment

The pharmacokinetics of the 5-HT3 receptor antagonist ondansetron were investigated following a single 8 mg intravenous dose given over 5 min in 19 patients with varying degrees of hepatic impairment and in six young healthy subjects. In comparison with the healthy controls, the patients with severe hepatic impairment had a lower mean plasma clearance (96 ml min-1 vs 478 ml min-1) and increased AUC (1383 ng ml-1 h vs 279 ng ml-1 h) and t1/2 (21 h vs 3.6 h). These differences were all statistically significant (P < 0.001). The corresponding values for patients with mild or moderate hepatic impairment fell between these extremes. Vss was greater in all patient groups than the control group, but the magnitude of the change was smaller than for the other parameters and did not reflect the increasing severity of hepatic impairment. There were no significant changes in Cmax. There were no drug-related adverse events in the patients studied. It is recommended that the dosing frequency of ondansetron be limited to once daily in patients with severe hepatic impairment.

Disposition of antipyrine in patients with extensive metastatic liver disease

In the present study the effect of metastatic liver disease on hepatic drug metabolism has been examined by studying the pharmacokinetics of antipyrine and the urinary excretion of antipyrine and its three major metabolites (4-hydroxyantipyrine, norantipyrine, and 3-hydroxymethylantipyrine) in 12 patients with extensive metastatic liver disease, and in 12 matched healthy controls. In the patients total liver volume, the volume of the liver parenchyma, and the volume of the liver metastases were determined by computed tomography. The volume of liver metastases always exceeded 35% of the total liver volume. There were no significant differences between the patients and controls in plasma half-life, plasma clearance, or apparent volume of distribution of antipyrine. The cumulative urinary excretion of antipyrine and its three major metabolites was significantly lower in patients [44 (18) %] than in controls [71 (8) %]. The excretion of antipyrine itself was unchanged and the decrease in cumulative excretion was due to reduced excretion of the three metabolites. The results show that the activity of the hepatic mixed function oxidases was not impaired even in patients with extensive metastatic liver disease. This may be because liver metastases do not cause a corresponding reduction in the volume of normal hepatic parenchyma. The decreased urinary excretion of the three major metabolites of antipyrine, which are mainly glucuronidated, may have been due to an alteration in the process of conjugation.

Bromosulfophthalein disposition in chronically bile duct obstructed rats

The disposition of bromosulfophthalein was studied in chronically bile duct obstructed rats. In this model a catheter was inserted into the common bile duct and the distal tip was sealed. Resumption of bile flow was achieved with great ease. Obstruction of bile duct for 18 days in rats resulted in elevated bilirubin, ALT, AST, and alkaline phosphatase levels. Portal hypertension developed within this period (11.6 +/- 0.5 in obstructed rats vs. 8.6 +/- 0.6 mm Hg in sham-operated group). After the bile duct obstruction was opened, the half-life time for elimination of bromosulfophthalein (42.30 +/- 6.47 min) was longer than in sham-operated rats (21.23 +/- 3.34 min). Plasma clearance was reduced by 70% in bile duct obstructed rats. In spite of increased bile flow rate, biliary excretion of the dye was reduced by 40% in chronically bile duct obstructed rats. Hepatic glutathione levels were significantly reduced by 20% in this model. The specific activity of glutathione S-transferase with chlorodinitrobenzene and styrene oxide, as substrates, was reduced by 50% and 30%, respectively. However, the percent of conjugated bromosulfophthalein in bile was similar to that of sham-operated rats.

Both phenolic and acyl glucuronidation pathways of diflunisal are impaired in liver cirrhosis

The pharmacokinetics of diflunisal, a salicylate derivative that undergoes phenolic and acyl glucuronidation as well as sulphate conjugation, has been studied after a single oral dose (250 mg) in patients with cirrhosis (n = 5) and in healthy controls (n = 5). The plasma clearance of total (bound + unbound) diflunisal was 10.2 ml.min-1 in the control subjects and it was not affected by cirrhosis (10.9 ml.min-1). The plasma protein binding of diflunisal was significantly reduced in cirrhosis; the percentage of unbound diflunisal in plasma was 0.089 in the controls and 0.147 in the patients with cirrhosis. Plasma clearance of unbound diflunisal was significantly impaired in cirrhosis: 11.5 l.min-1 in control subjects vs 7.41.min-1 in cirrhotics. In cirrhotic patients, the unbound partial clearances to the phenolic and acyl glucuronides were both significantly reduced, by approximately 38%. The unbound partial clearance to the sulphate conjugate was not significantly affected by cirrhosis. The results show that both the phenolic and acyl glucuronidation pathways of diflunisal are equally susceptible to the effects of liver cirrhosis.

The production of hepatic cirrhosis in rats

This study investigated the conditions necessary to produce a predictable yield of cirrhosis in rats. A previously published method, using carbon tetrachloride, was used as a basis for the study. Histopathology was used in a semi-quantitative manner to examine which observations could be used for the prediction of progression and final yield of cirrhosis. A comparison of different vehicles for oral carbon tetrachloride administration showed no effect of vehicle on the final yield of cirrhosis. Also, there were no observations during the study that should be used for prediction. Variability in the severity of hepatic impairment is an inherent feature of this model, and supporting histopathology is essential. We recommend a simple protocol for the initiation of cirrhosis in rats using carbon tetrachloride.

Pharmacokinetics of metoclopramide in patients with liver cirrhosis

The pharmacokinetics of metoclopramide were investigated after intravenous and oral administration in eight patients with severe alcoholic cirrhosis and in eight healthy volunteers. As a consequence of a 50% lower clearance (0.16 +/- 0.07 vs 0.34 +/- 0.09 l h-1 kg-1, plasma drug concentrations and the half-life of metoclopramide were greater in patients following both routes of drug administration. Volume of distribution (3.1 +/- 0.8 vs 3.4 +/- 1.2 l kg-1) and absolute bioavailability (79 +/- 19 vs 84 +/- 15%) were similar in the two groups. The adverse effects of metoclopramide observed in patients with marked hepatic impairment are likely to result from increased accumulation of the drug as a result of impaired clearance. Consequently a reduction in dose of 50% is recommended in patients with severe liver cirrhosis.

Drug glucuronidation in humans

Glucuronidation is a major metabolic pathway for a large number of drugs in humans. Conjugation of drugs and other chemicals with glucuronic acid is catalyzed by the multigene UDP-glucuronosyltransferase family. It is believed that a number (unspecified at present) of glucuronosyltransferase isozymes, which probably differ in terms of substrate specificity and regulation, contribute to drug glucuronidation. Factors known to influence the pharmacokinetics of glucuronidated drugs in man, presumably via an effect on specific glucuronosyltransferases, include age (especially the neonatal period), cigarette smoking, diet, certain disease states, coadministered drugs, ethnicity, genetics and hormonal effects.

Conjugation pathways in liver disease

1. The activities of microsomal glucuronyltransferase and thiomethyltransferase, and those of cytosolic sulphotransferase, acetyltransferase, glutathione transferase and thiomethyltransferase were measured in abnormal (cirrhosis and chronic hepatitis) and normal livers. 2. Glucuronyltransferase and sulphotransferase were investigated with 2-naphthol and ethinyloestradiol as substrates. p-Aminobenzoic acid, benzo(a)pyrene-4,5-epoxide and 2-mercaptoethanol were the substrates of acetyltransferase, glutathione transferase and thiomethyltransferase, respectively. 3. Enzyme activities are expressed as nmol min-1 incubation mg-1 protein and the averages (+/- s.d.) are given. With 2-naphthol as substrate, the glucuronyltransferase activity was 6.55 +/- 4.10 (abnormal liver, n = 33) and 7.81 +/- 4.02 (normal liver, n = 26) (NS); whereas sulphotransferase activity was 0.28 +/- 0.18 (abnormal liver, n = 35) and 0.68 +/- 0.43 (normal liver, n = 26) (P less than 0.01). Glucuronyltransferase activity towards ethinyloestradiol was 102.5 +/- 56.9 (abnormal liver, n = 30) and 107 +/- 59.9 (normal liver, n = 26) (NS), whereas sulphotransferase activity was 57.2 +/- 36.0 (abnormal liver, n = 35) and 122 +/- 67.6 (normal liver, n = 28) (P less than 0.01). Acetyltransferase activity was 0.84 +/- 0.83 (abnormal liver, n = 35) and 3.84 +/- 1.65 (normal liver, n = 26) (P less than 0.01). Glutathione transferase activity was 0.83 +/- 0.68 (abnormal liver, n = 35) and 2.90 +/- 1.59 (normal liver, n = 25) (P less than 0.01) and thiomethyltransferase activity was 1.00 +/- 0.69 (abnormal liver, n = 34) and 3.99 +/- 1.49 (normal liver, n = 25) (P less than 0.01). 4. Liver disease lowers the activities towards the substrates studied of sulphotransferase, acetyltransferase, glutathionetransferase and thiomethyltransferase but not that of glucuronyltransferase.(ABSTRACT TRUNCATED AT 250 WORDS)