Genetic predisposition to drug-induced hepatotoxicity

Keeping patients in the dark: perioperative anesthetic considerations for patients receiving 5-aminolevulinic acid for glioma resection

PURPOSE OF REVIEW

5-Aminolevulinic acid hydrochloride (5-ALA), available under the trade name Gleolan, is an orally administered fluorophore drug used to enhance visual differentiation of cancerous tissue from healthy tissue, primarily during surgical resection of high-grade gliomas. Although given preoperatively, 5-ALA has important implications for anesthetic care throughout the perioperative period. This article reviews pharmacology, safety concerns, and perioperative considerations for patients who receive oral 5-ALA.

RECENT FINDINGS

Although approved for clinical use by the United States Food and Drug Administration in 2017, studies and case reports published since then have further delineated side effects of this medication and its mechanisms and pharmacokinetics.

SUMMARY

Mitigating the possible side effects of 5-ALA requires an understanding of its basic mechanism as well as focused perioperative planning and communication. Administration of this medication may result in nausea, vomiting, photosensitivity, increase in serum concentration of liver enzymes, and hypotension. Patients who receive 5-ALA must be protected from prolonged light exposure during the first 48 h after consumption and administration of other photosensitizing agents should be avoided (Supplemental Video File/Video abstract).

Sterile inflammation in liver transplantation

Sterile inflammation is the immune response to damage-associated molecular patterns (DAMPs) released during cell death in the absence of foreign pathogens. In the setting of solid organ transplantation, ischemia-reperfusion injury results in mitochondria-mediated production of reactive oxygen and nitrogen species that are a major cause of uncontrolled cell death and release of various DAMPs from the graft tissue. When properly regulated, the immune response initiated by DAMP-sensing serves as means of damage control and is necessary for initiation of recovery pathways and re-establishment of homeostasis. In contrast, a dysregulated or overt sterile inflammatory response can inadvertently lead to further injury through recruitment of immune cells, innate immune cell activation, and sensitization of the adaptive immune system. In liver transplantation, sterile inflammation may manifest as early graft dysfunction, acute graft failure, or increased risk of immunosuppression-resistant rejection. Understanding the mechanisms of the development of sterile inflammation in the setting of liver transplantation is crucial for finding reliable biomarkers that predict graft function, and for development of therapeutic approaches to improve long-term transplant outcomes. Here, we discuss the recent advances that have been made to elucidate the early signs of sterile inflammation and extent of damage from it. We also discuss new therapeutics that may be effective in quelling the detrimental effects of sterile inflammation.

Pharmacogenomics, concepts for the future of perioperative medicine and pain management: A review

Pharmacogenomics is the study of how genetic differences between individuals affect pharmacokinetics and pharmacodynamics. These differences are apparent to clinicians when taking into account the wide range of responses to medications given in clinical practice. A review of literature involving pharmacogenomics and pain management was performed. The implementation of preoperative pharmacogenomics will allow us to better care for our patients by delivering personalized, safer medicine. This review describes the current state of pharmacogenomics as it relates to many aspects of clinical practice and how clinicians can use these tools to improve patient outcomes.

Are genetic variations in glutathione S-transferases involved in anti-tuberculosis drug-induced liver injury? A meta-analysis

WHAT IS KNOWN AND OBJECTIVE

As a crucial protective role in the detoxifying mechanisms of drugs, glutathione S-transferases (GSTs) may affect an individual patient's susceptibility to anti-tuberculosis drug-induced liver injury (ATLI). However, the results of studies investigate the association between GSTM1, GSTT1 and GSTP1 polymorphisms and risk of ATLI are inconclusive. A meta-analysis on this topic was performed.

METHODS

PubMed, EMBASE, ISI web of science and the Chinese National Knowledge Infrastructure (CNKI) were systematically searched to identify relevant studies. Odds ratios (ORs) with corresponding 95% confidence intervals (CIs) were calculated. Heterogeneity among articles and publication bias were also tested.

RESULTS AND DISCUSSION

After excluding one study as an outlier, the null GSTM1 genotype was associated with an increased risk of ATLI (OR = 1.270, 95% CI (1.014-1.590, P = .038), especially in East Asians (OR = 1.501, 95% CI (1.303-1.730). With similar exclusion, the null GSTT1 genotype increased the risk of ATLI in the total population (OR = 1.169, 95% CI: 1.028-1.330) and in Indians (OR = 1.732, 95% CI: 1.229-2.416). No statistically significant association was observed between the mutant GSTP1 genotype with risk of ATLI, which may need more rigorous and uniform case-control or cohort studies for more robust inferences.

WHAT IS NEW AND CONCLUSION

This up-to-date meta-analysis strongly suggests associations of GSTM1 and GSTT1 polymorphisms with ATLI. The results show the increased risk of ATL1 with the null GSTM1 and GSTT1 genotype on ATLI development. No such association is shown with the mutant GSTP1 genotype.

Evaluation of the risk of liver damage from the use of 5-aminolevulinic acid for intra-operative identification and resection in patients with malignant gliomas

BACKGROUND

The clinical efficacy of 5-aminolevulinic acid (5-ALA) for fluorescence-guided surgery of malignant gliomas is evident from several studies; however, as post-operative elevations of liver enzymes have been seen, there is a potential risk of liver damage upon administration. The aim of the present study was to assess the potential risk of liver damage and investigate liver enzyme reactions of patients going through 5-ALA-guided operations to improve the monitoring of their operations.

METHODS

A retrospective study of all patients undergoing 5-ALA-guided surgery during a 2-year period (September 2012-September 2014) at the University Hospital of Copenhagen, Rigshospitalet, was conducted. All patients received a pre-operative dose of 20 mg/kg bodyweight 5-ALA. The pre- and post-operative enzyme levels of alanine aminotransferase, aspartate aminotransferase, gamma glutamyltransferase and amylase of both men and women, respectively, were evaluated.

RESULTS

Ninety-nine adults met the inclusion criteria. Fifty patients had one or multiple temporary post-operative elevations of their liver enzymes. The mean post-operative values were not increased, except for a brief elevation of gamma-glutamyltransferase levels in women. No registrations of liver impairment or clinical signs of liver failure were observed.

CONCLUSIONS

The findings suggest that the administration of 5-ALA or the combined effect of 5-ALA, anaesthesia and tumour resection can cause a mild and reversible elevation in liver enzymes. It therefore appears safe to change the regime of monitoring. Routine blood samples are thus abolished, though caution remains necessary in patients with known liver impairment.

Drug Induced Liver Injury: Review with a Focus on Genetic Factors, Tissue Diagnosis, and Treatment Options

Drug-induced liver injury (DILI) is a rare but potentially life threatening adverse drug reaction. DILI may mimic any morphologic characteristic of acute or chronic liver disease, and the histopathologic features of DILI may be indistinguishable from those of other causes of liver injury, such as acute viral hepatitis. In this review article, we provide an update on causative agents, clinical features, pathogenesis, diagnosis modalities, and outcomes of DILI. In addition, we review results of recently reported genetic studies and updates on pharmacological and invasive treatments.

Drug-induced autoimmune liver disease: A diagnostic dilemma of an increasingly reported disease

The aetiology of autoimmune hepatitis (AIH) is uncertain but the disease can be triggered in susceptible patients by external factors such as viruses or drugs. AIH usually develops in individuals with a genetic background mainly consisting of some risk alleles of the major histocompatibility complex (HLA). Many drugs have been linked to AIH phenotypes, which sometimes persist after drug discontinuation, suggesting that they awaken latent autoimmunity. At least three clinical scenarios have been proposed that refers to drug- induced autoimmune liver disease (DIAILD): AIH with drug-induced liver injury (DILI); drug induced-AIH (DI-AIH); and immune mediated DILI (IM-DILI). In addition, there are instances showing mixed features of DI-AIH and IM-DILI, as well as DILI cases with positive autoantibodies. Histologically distinguishing DILI from AIH remains a challenge. Even more challenging is the differentiation of AIH from DI-AIH mainly relying in histological features; however, a detailed standardised histologic evaluation of large cohorts of AIH and DI-AIH patients would probably render more subtle features that could be of help in the differential diagnosis between both entities. Growing information on the relationship of drugs and AIH is being available, being drugs like statins and biologic agents more frequently involved in cases of DIAILD. In addition, there is some evidence on the fact that patients diagnosed with DIAILD may have had a previous episode of hepatotoxicity. Further collaborative studies in DIAILD will strengthen the knowledge and understanding of this intriguing and complex disorder which might represent different phenotypes across the spectrum of disease.

Herb-induced autoimmune-like hepatitis in C57BL/6J mice

BACKGROUND & AIMS

Animal model suitable for studying herb-induced experimental autoimmune hepatitis (AIH) remains a challenging problem. A medicinal herb containing Scutellaria baicalensis Georgi (Sb) and Bupleurum chinense DC (Bc) has been sporadically reported to be related to liver fibrosis. The aim of this study was to investigate the effects of Sb and Bc on experimental AIH in mice.

METHODS

C57BL/6J mice received intraperitoneal injection of Sb and/or Bc herbal extracts (1 mg/kg) for 4 or 8 weeks. Serum samples were collected to analyse serum transferase (AST, ALT), creatinine, markers for AIH and hepatic cytokine levels such as IFN-γ, IL10 and TGF-β1. Peripheral mononuclear cell (PBMC) gene expression profiles were analysed to show their effects on immune system.

RESULTS

Our results showed that Sb or Bc treatment increased serum AST, ALT, IgG and ANA levels. Prominent necroinflammatory changes were demonstrated in the livers of Sb- or Bc-treated mice while the decrease in IFN-γ and elevation of IL10 and TGF-β1 levels in liver tissues. Furthermore, the PMBC gene expression profile suggested that Sb or Bc treatment could modulate immune responses.

CONCLUSION

We conclude that the presence of AIH in Sb- or Bc-treated mice and C57BL/6J strain mice is a reliable animal model for studying herb-induced AIH-like hepatitis.

Transcriptomic hepatotoxicity signature of chlorpromazine after short- and long-term exposure in primary human sandwich cultures

Drug-induced liver injury is the most frequent reason for market withdrawal of approved drugs, and is difficult to predict in animal models. Here, we analyzed transcriptomic data derived from short- and long-term cultured primary human hepatocytes (PHH) exposed to the well known human hepatotoxin chlorpromazine (CPZ). Samples were collected from five PHH cultures after short-term (1 and 3 days) and long-term (14 days) repeat daily treatment with 0.1 or 0.2 µM CPZ, corresponding to C(max). Two PHH cultures were additionally treated with 1 µM CPZ, and the three others with 0.02 µM CPZ. Differences in the total number of gene changes were seen between donors and throughout treatment. Specific transcriptomic hepatotoxicity signatures were created for CPZ and consisted of inflammation/hepatitis, cholestasis, and liver proliferation in all five donors, as well as fibrosis and steatosis, which were observed in four of five donors. Necrosis was present in three of five donors, and an indicative signature of cirrhosis was observed after long-term 14-day repeat treatment, also in three of five donors. The inter-donor variability in the inflammatory response to CPZ treatment was associated with variability in the strength of the response of the transcriptomic hepatotoxicity signatures, suggesting that features of inflammation could be related to the idiosyncratic hepatotoxic effects of CPZ in humans.

Glutathione metabolism modeling: a mechanism for liver drug-robustness and a new biomarker strategy

BACKGROUND

Glutathione metabolism can determine an individual's ability to detoxify drugs. To increase understanding of the dynamics of cellular glutathione homeostasis, we have developed an experiment-based mathematical model of the kinetics of the glutathione network. This model was used to simulate perturbations observed when human liver derived THLE cells, transfected with human cytochrome P452E1 (THLE-2E1 cells), were exposed to paracetamol (acetaminophen).

METHODS

Human liver derived cells containing extra human cytochrome P4502E1 were treated with paracetamol at various levels of methionine and in the presence and absence of an inhibitor of glutamyl-cysteine synthetase (GCS). GCS activity was also measured in extracts. Intracellular and extracellular concentrations of substances involved in glutathione metabolism were measured as was damage to mitochondria and proteins. A bottom up mathematical model was made of the metabolic pathways around and including glutathione.

RESULTS

Our initial model described some, but not all the metabolite-concentration and flux data obtained when THLE-2E1 cells were exposed to paracetamol at concentrations high enough to affect glutathione metabolism. We hypothesized that the lack of correspondence could be due to upregulation of expression of glutamyl cysteine synthetase, one of the enzymes controlling glutathione synthesis, and confirmed this experimentally. A modified model which incorporated this adaptive response adequately described the observed changes in the glutathione pathway. Use of the adaptive model to analyze the functioning of the glutathione network revealed that a threshold input concentration of methionine may be required for effective detoxification of reactive metabolites by glutathione conjugation. The analysis also provided evidence that 5-oxoproline and ophthalmic acid are more useful biomarkers of glutathione status when analyzed together than when analyzed in isolation, especially in a new, model-assisted integrated biomarker strategy.

CONCLUSION

A robust mathematical model of the dynamics of cellular changes in glutathione homeostasis in cells has been developed and tested in vitro.

GENERAL SIGNIFICANCE

Mathematical models of the glutathione pathway that help examine mechanisms of cellular protection against xenobiotic toxicity and the monitoring thereof, can now be made.

Drug-induced liver injury: the role of drug metabolism and transport

Many studies have pinpointed the significant contribution of liver-mediated drug metabolism and transport to the complexity of drug-induced liver injury (DILI). Phase I cytochrome P450 (CYP450) enzymes can lead to altered drug metabolism and formation of toxic metabolites, whilst Phase II enzymes are also associated with DILI. The emerging role of hepatic transporters in regulating the movement of endogenous and exogenous chemicals (e.g., bile acids and drugs) across cellular and tissue membranes is critical in determining the pathophysiology of liver disease as well as drug toxicity and efficacy. Genetic and environmental factors can have a significant impact on drug metabolism and transporter proteins, consequently increasing the risk of DILI in susceptible individuals. The assessment of these factors therefore represents an important approach for predicting and preventing DILI, by better understanding the pharmacological profile of a specific drug. This review focuses on the mechanisms of DILI associated with drug metabolism and hepatic transport, and how they can be influenced by underlying factors.

Predicting and preventing acute drug-induced liver injury: what's new in 2010?

IMPORTANCE OF THE FIELD

The field of drug-induced liver injury (DILI) continues to expand in terms of global registries and with new agents added every year. Given the need to improve on our current methods of preclinical testing and monitoring for DILI during both clinical trials and in the post-approval setting, there is increasing research aimed at better understanding why injury occurs and who is most susceptible. To this end, the active pursuit of biomarkers that will predict injury prior to its occurrence and genetic testing that can identify individuals at risk of DILI continue to be at the forefront.

AREAS COVERED IN THIS REVIEW

While alanine aminotransferase (ALT) testing remains the workhorse of biochemical monitoring, it only detects hepatic injury after it has occurred and, therefore, is not a true predictor. The utility and shortcomings of ALT and other liver tests are reviewed along with a synopsis of several other candidate biomarkers that are being studied. In addition, we review the recent data supporting testing for genetic predisposition to DILI and how identifying clinical risk factors may translate into better means for preventing DILI.

WHAT THE READER WILL GAIN

We update the basis on which age and gender are considered risk factors for DILI, and review the latest reports detailing the association of several candidate genes and the development of DILI in a susceptible patient. Human leukocyte antigen-B*5701 is closely linked to the hypersensitivity reaction seen with abacavir, and such screening has been successfully incorporated into HIV treatment around the globe and offers the promise that testing for other genetic markers will soon become a routine part of clinical practice. At present, candidate genes conferring specific susceptibility to DILI have been identified for a relatively few agents (e.g., flucloxacillin, amoxicillin-clavulanate, ximelagatran and isoniazid), but many more are under study. Preventing DILI often comes down to avoiding the use of potentially hepatotoxic drugs in certain situations, and we review the clinical scenarios in which this is most relevant.

TAKE HOME MESSAGE

Given the number and range of studies aimed at identifying predictors of DILI, the focus of this review is to summarize what we consider to be the most relevant new information published on the topics of clinical and genetic factors that predispose to DILI, the use of biomarkers as predictors of acute DILI, along with advances in prevention strategies.

Black Cohosh Hepatic Safety: Follow-Up of 107 Patients Consuming a Special Cimicifuga racemosa rhizome Herbal Extract and Review of Literature

European Medicines Agency (EMEA) and the Committee on Herbal Medicinal Products (HMPC) on July 2006 have released an alert to get European sanitary authorities aware of 42 cases of suspected hepatotoxic reactions in patients consuming Cimicifuga racemosa rhizome. In the public statement EMEA itself considered reliable as hepatotoxic reactions only four cases, on the base of RUCAM score: two were considered possible and two probable. Lacking in almost all of them a precise description of cases, especially a botanical-chemical analysis of the suspected substance, we think there is no real proof of supposed C. racemosa rhizome hepatotoxicity. In our department we administer from about 10 years C. racemosa as special herbal dry extract as single substance or mixed with other medicinal plants at the dose of 500–1000 mg daily, for treatment of menopause related disorders without any reported adverse effect. After EMEA's official signal we have contacted all our patients using a C. racemosa rhizome herbal extract continuously from more than 12 months to verify possible hepatotoxic effects. We followed-up 107 women, and asked them by telephone (33/107) and/or after anamnesis and clinical examination (74/107) to undergo a blood sample examination. In all the patients there was no sign of hepatic disease, or worsening of already altered but stable parameters. We think on the base of these data and current literature C. racemosa rhizome extract should not be considered a potential hepatotoxic substance.

Increased risk of hospitalization for acute hepatitis in patients with previous exposure to NSAIDs

BACKGROUND

Epidemiological studies related to hospitalization due to the hepatotoxicity of traditional non-steroidal anti-inflammatory drugs (NSAIDs) are infrequent, and case reports of hepatotoxicity of nimesulide, celecoxib, and rofecoxib seem to be increasing. The reimbursement database of National Health Insurance (NHI) in Taiwan provided an opportunity for post-marketing surveillance. We conducted this study to determine the association between the use of hepatoxic NSAIDs and increased hospitalizations related to acute hepatitis.

METHODS

We included hospitalized subjects with a major diagnosis of acute or sub-acute necrosis of liver or toxic hepatitis and excluded viral and other causes of hepatobiliary diseases from the NHI database from 1 April 2001 to 31 December 2004. We applied two kinds of models to analyze by uni-directional and bi-directional case-crossover designs during the 28 days exposure periods and performed conditional logistic regression models.

RESULTS

There were 4519 cases of hospitalization relating to acute hepatitis, and the odds ratios of celecoxib, nimesulide, dicofenac, ibuprofen, and other hepatoxic NSAIDs were significantly increased. Compared with the adjusted odds ratios of other hepatoxic NSAIDs (OR = 2.13, 95%CI = 2.00, 2.28), celecoxib (OR =1.92, 95%CI = 1.38, 2.69) was similar during the 28 days by our uni-directional case-crossover design.

CONCLUSIONS

Our results provide evidence for an increased risk of hospitalization with acute hepatitis among hepatoxic NSAIDs including celecoxib users. Further mechanistic research is warranted in order to document celecoxib's hepatotoxicity.

Drug-induced liver injury: insights from genetic studies

Drug-induced liver injury (DILI) is an increasing health problem and a challenge for physicians, regulatory bodies and the pharmaceutical industry, not only because of its potential severity and elusive pathogenesis but also because it is often inaccurately diagnosed, commonly missed entirely and more often not reported. The general view is that idiosyncratic DILI, which is not predictable whether based on the pharmacology of the drug or on the dose administered, is determined by the presence in the recipient of variants in, or expression of, genes coding for key metabolic pathways and/or the immune response, and the interaction of these genetic variants with environmental variables. Furthermore, idiosyncratic DILI is an example of a complex-trait disease with two or more susceptibility loci, as reflected by the frequency of genetic variants in the population often being higher than the occurrence of significant liver injury. Polymorphisms of bioactivation/toxification pathways via the CYP450 enzymes (Phase I), detoxification reactions (Phase II) and excretion/transport (Phase III), together with immunological factors that might determine DILI are reviewed. Challenges such as gene-trait association studies and whole-genome studies, and future approaches to the study of DILI are explored. Better knowledge of the candidate genes involved could provide further insight for the prospective identification of susceptible patients at risk of developing drug-induced hepatotoxicity, development of new diagnostic tools and new treatment strategies with safer drugs.

Health maintenance issues in cirrhosis

Caring for patients with cirrhosis requires special consideration. The role of the hepatologist is to assist the primary care physician in caring for such patients. This involves an active role in immunizations, lifestyle modifications, and providing instructions on when to go to the emergency room (ER). There are also specific recommendations geared toward the patient with cirrhosis relating to slowing down the disease process, maintaining quality of life, and improving survival.

A benefit-risk assessment of benzbromarone in the treatment of gout. Was its withdrawal from the market in the best interest of patients?

Benzbromarone, a potent uricosuric drug, was introduced in the 1970s and was viewed as having few associated serious adverse reactions. It was registered in about 20 countries throughout Asia, South America and Europe. In 2003, the drug was withdrawn by Sanofi-Synthélabo, after reports of serious hepatotoxicity, although it is still marketed in several countries by other drug companies. The withdrawal has greatly limited its availability around the world, and increased difficulty in accessing it in other countries where it has never been available.The overall aim of this paper is to determine if the withdrawal of benzbromarone was in the best interests of gouty patients and to present a benefit-risk assessment of benzbromarone. To determine this, we examined (i) the clinical benefits associated with benzbromarone treatment and compared them with the success of alternative therapies such as allopurinol and probenecid, particularly in patients with renal impairment; (ii) the attribution of the reported cases of hepatotoxicity to treatment with benzbromarone; (iii) the incidence of hepatotoxicity possibly due to benzbromarone; (iv) adverse reactions to allopurinol and probenecid. From these analyses, we present recommendations on the use of benzbromarone.Large reductions in plasma urate concentrations in patients with hyperuricaemia are achieved with benzbromarone and most patients normalize their plasma urate. The half-life of benzbromarone is generally short (about 3 hours); however, a uricosuric metabolite, 6-hydroxybenzbromarone, has a much longer half-life (up to 30 hours) and is the major species responsible for the uricosuric activity of benzbromarone, although its metabolism by cytochrome P450 (CYP) 2C9 in the liver may vary between patients as a result of polymorphisms in this enzyme. It is effective in patients with moderate renal impairment. Standard dosages of benzbromarone (100 mg/day) tend to produce greater hypouricaemic effects than standard doses of allopourinol (300 mg/day) or probenecid (1000 mg/day).Adverse effects associated with benzbromarone are relatively infrequent, but potentially severe. Four cases of benzbromarone-induced hepatotoxicity were identified from the literature. Eleven cases have been reported by Sanofi-Synthélabo, but details are not available in the public domain. Only one of the four published cases demonstrated a clear relationship between the drug and liver injury as demonstrated by rechallenge. The other three cases lacked incontrovertible evidence to support a diagnosis of benzbromarone-induced hepatotoxicity. If all the reported cases are assumed to be due to benzbromarone, the estimated risk of hepatotoxicity in Europe was approximately 1 in 17 000 patients but may be higher in Japan.Benzbromarone is also an inhibitor of CYP2C9 and so may be involved in drug interactions with drugs dependent on this enzyme for clearance, such as warfarin. Alternative drugs to benzbromarone have significant adverse reactions. Allopurinol is associated with rare life-threatening hypersensitivity syndromes; the risk of these reactions is approximately 1 in 56 000. Rash occurs in approximately 2% of patients taking allopurinol and usually leads to cessation of prescription of the drug. Probenecid has also been associated with life-threatening reactions in a very small number of case reports, but it frequently interacts with many renally excreted drugs. Febuxostat is a new xanthine oxidoreductase inhibitor, which is still in clinical trials, but abnormal liver function is the most commonly reported adverse reaction.Even assuming a causal relationship between benzbromarone and hepatotoxicity in the identified cases, benefit-risk assessment based on total exposure to the drug does not support the decision by the drug company to withdraw benzbromarone from the market given the paucity of alternative options. It is likely that the risks of hepatotoxicity could be ameliorated by employing a graded dosage increase, together with regular monitoring of liver function. Determination of CYP2C9 status and consideration of potential interactions through inhibition of this enzyme should be considered. The case for wider and easier availability of benzbromarone for treating selected cases of gout is compelling, particularly for patients in whom allopurinol produces insufficient response or toxicity.We conclude that the withdrawal of benzbromarone was not in the best interest of patients with gout.

The pharmacologic basis of ifosfamide use in adult patients with advanced soft tissue sarcomas

The treatment outcome of patients with locally advanced and metastatic soft tissue sarcomas is poor. Doxorubicin is regarded as standard treatment, but its use is featured by the occurrence of cardiotoxicity. This hinders the administration of this drug at high doses or in combination with, in theory, attractive newly developed targeted drugs, such as vascular endothelial growth factor (VEGF) pathway inhibitors. The combination of doxorubicin and VEGF pathway inhibitors has been shown to yield an unacceptable high rate of cardiomyopathy. Ifosfamide is the only drug that consistently shows response rates comparable to those of doxorubicin. The lack of cardiotoxicity renders this drug a much more attractive alternative than doxorubicin to be explored at high doses or as part of new drug combinations. This review addresses the clinical pharmacology, metabolism, and present role of ifosfamide in the treatment of locally advanced and/or metastatic soft tissue sarcomas, excluding gastrointestinal stromal tumors, the Ewing-like sarcomas, and other small blue round cell tumors. Furthermore, this review focuses on the anticipated growing role of ifosfamide in the development of new treatment strategies.

Association between tetracycline or doxycycline and hepatotoxicity: a population based case-control study

BACKGROUND AND OBJECTIVE

An FDA Working Group, along with representatives of PhRMA and the American Association for the Study of Liver Diseases, as well as the Institute of Medicine Report 'To Err is Human: Building a Safer Health Care System' have suggested that post-marketing drug surveillance is a important method to decrease adverse drug events. While tetracyclines are known to cause hepatotoxicity, no post-marketing drug surveillance studies have examined the risk of developing hepatotoxicity with tetracyclines. Therefore, the objective of this study is to determine the difference in risk of hepatotoxicity in patients receiving doxycycline or tetracycline using California Medicaid claims.

METHODS

This study used a retrospective, matched case-control study using California Medicaid claims data. The cases were defined as recipients who had at least one diagnosis of hepatotoxicity any time from 1 July 1999 to 31 December 2001. One control was identified for each case, matched on age, gender and race. Logistic regression was used to determine the adjusted odds ratio (OR) and 95% confidence intervals for current users and past users of tetracycline and doxycycline. Covariates controlled for in the analysis were age, use of other hepatotoxic drugs, renal dysfunction, pregnancy, and alcohol or illicit drug use.

RESULTS

A total of 3377 cases of hepatotoxicity were identified. Current users and past users of tetracycline had a statistically significant increased risk of developing hepatotoxicity (current use OR 3.70, 95% CI 1.19-11.45; past use OR 2.72, 95% CI 1.26-5.85). Current users or past users of doxycycline did not have an increased risk of developing hepatotoxicity (current use OR 1.49, 95% CI 0.61-3.62; past use OR 1.74, 95% CI 0.99-3.06). Tetracycline was commonly used for acne, acute bronchitis and upper respiratory infections. Doxycycline was commonly used for acute bronchitis, vaginitis and acne.

DISCUSSION AND CONCLUSION

Doxycycline was potentially less hepatotoxic than tetracycline. Doxycycline could potentially be a safe substitute for tetracycline, when appropriate.

Drug-induced liver injury

Drug-induced liver injury is a frequent cause of hepatic dysfunction. Reliably establishing whether the liver disease was caused by a drug requires the exclusion of other plausible causes and the search for a clinical drug signature. The drug signature consists of the pattern of liver test abnormality, the duration of latency to symptomatic presentation, the presence or absence of immune-mediated hypersensitivity and the response to drug withdrawal. Determination of causality also includes an evaluation of individual susceptibility to drug-induced liver injury. This susceptibility is governed by both genetic and environmental factors. Components of the drug signature in conjunction with certain risk factors have been incorporated into formal scoring systems that are predictive of the likelihood of drug-induced liver injury. The most validated scoring system is the Roussel-Uclaf causality assessment method, which nonetheless retains certain imperfections. Mitigating the potential for drug-induced liver injury is achieved by the identification of toxicity signals during clinical trials and the monitoring of liver tests in clinical practice. There are three signals of liver toxicity in clinical trials: (i) a statistically significant doubling (or more) in the incidence of serum alanine aminotransferase (ALT) elevation >3 x the upper limit of normal (ULN); (ii) any incidence of serum ALT elevation >8-10 x ULN; and (iii) any incidence of serum ALT elevation >3 x ULN accompanied by a serum bilirubin elevation >2 x ULN. Monitoring of liver tests in clinical practice has shown unconvincing efficacy, but where a benefit-risk analysis would favour continued therapy, monthly monitoring may have some benefit compared with no monitoring at all. With rare exception, treatment of drug-induced liver injury is principally supportive. Drug toxicity is the most common cause of acute liver failure, defined as a prolonged prothrombin time (international normalised ratio > or =1.5) and any degree of mental alteration occurring <26 weeks after the onset of illness in a patient without pre-existing cirrhosis. A patient who meets these criteria must be evaluated for liver transplantation. The pathogenesis of drug-induced liver injury can be examined on the basis of the two principal patterns of injury. The hepatocellular pattern is characterised by a predominant rise in the level of transaminases and results from the demise of hepatocytes by means of either apoptosis or necrosis. The cholestatic pattern is characterised by a predominant rise of the serum alkaline phosphatase level and usually results from injury to the bile ductular cells either directly by the drug or its metabolite, or indirectly by an adaptive immune response.

Acetaminophen safety and hepatotoxicity--where do we go from here?

Acetaminophen has been widely used for > 50 years in the treatment of pain and fever and provides for the safe and effective relief of these symptoms. In a small minority of patients, however, acetaminophen is responsible for life-threatening liver injury and accounts for up to 50% of all adult cases of acute liver failure in the US. Although approximately two-thirds of adult overdoses are associated with suicide attempts, many are inadvertent, often due to the use of multiple acetaminophen formulations over many days. Additionally, some individuals appear to experience acetaminophen toxicity at 'therapeutic' doses of < 4 g/day, for reasons unknown. In pediatric populations, the overwhelming majority of acetaminophen overdoses are due to unintentional overdoses, except for the predominance of suicidal ingestions in the teenage population. This article seeks to review the mechanism and metabolism of acetaminophen and the features of toxicity in adults, pediatric and special populations. Additionally, expert opinion is presented herein to aid in reducing the frequency and severity of liver injury from acetaminophen.

Genetic polymorphisms of manganese superoxide dismutase, NAD(P)H:quinone oxidoreductase, glutathione S-transferase M1 and T1, and the susceptibility to drug-induced liver injury

BACKGROUND/AIMS

Drug metabolizing enzymes may be related to drug-induced liver injury (DILI). Manganese superoxide dismutase (MnSOD), NAD(P)H:quinone oxidoreductase (NQO1), and glutathione S-transferase (GST) are important drug metabolizing enzymes. We aimed to elucidate the relationship between genetic polymorphisms of these enzymes and the susceptibility to DILI.

METHODS

A total of 115 patients with DILI and 115 drug-, sex-, and age-matched controls were enrolled. Their genetic polymorphisms of MnSOD, NQO1, GSTM1, and GSTT1 were assayed.

RESULTS

Sixty-three (54.8%) of DILI patients were incriminated to anti-tuberculosis drugs. Subjects with a mutant C allele (T/C or C/C genotype) of MnSOD had a higher risk of DILI than those with MnSOD T/T genotype, both in overall drugs studied (adjusted OR: 2.44, 95% C.I.: 1.38-4.30, P=0.002), and in sub-category of anti-tuberculosis drugs (adjusted OR: 2.47, 95% C.I.: 1.13-5.39, P=0.02). In addition, subjects carrying GSTM1 null genotype had increased risk of anti-tuberculosis DILI (adjusted OR: 2.23, 95% C.I.: 1.07-4.67, P=0.03).

CONCLUSIONS

The MnSOD mutant C allele may increase the susceptibility to DILI, and GSTM1 null genotype may be related to anti-tuberculosis drug-induced hepatotoxicity. Determination of the MnSOD and GSTM1 genotypes may help identify patients at high risk for DILI.

Review article: drug hepatotoxicity

BACKGROUND

Drug toxicity is the leading cause of acute liver failure in the United States. Further understanding of hepatotoxicity is becoming increasingly important as more drugs come to market.

AIMS

(i) To provide an update on recent advances in our understanding of hepatotoxicity of select commonly used drug classes. (ii) To assess the safety of these medications in patients with pre-existing liver disease and in the post-liver transplant setting. (iii) To review relevant advances in toxicogenomics which contribute to the current understanding of hepatotoxic drugs.

METHODS

A Medline search was performed to identify relevant literature using search terms including 'drug toxicity, hepatotoxicity, statins, thiazolidinediones, antibiotics, antiretroviral drugs and toxicogenomics'.

RESULTS

Amoxicillin-clavulanic acid is one of the most frequently implicated causes of drug-induced liver injury worldwide. Statins rarely cause clinically significant liver injury, even in patients with underlying liver disease. Newer thiazolidinediones are not associated with the degree of liver toxicity observed with troglitazone. Careful monitoring for liver toxicity is warranted in patients who are taking antiretrovirals, especially patients who are co-infected with hepatitis B and C. Genetic polymorphisms among enzymes involved in drug metabolism and HLA types may account for some of the differences in individual susceptibility to drug hepatotoxicity.

CONCLUSIONS

Drug-induced hepatotoxicity will remain a problem that carries both clinical and regulatory significance as long as new drugs continue to enter the market. Future results from ongoing multicentre collaborative efforts may help contribute to our current understanding of hepatotoxicity associated with drugs.

Genetic polymorphisms of CYP2C9 and CYP2C19 are not related to drug-induced idiosyncratic liver injury (DILI)

BACKGROUND AND PURPOSE

The general view on the pathogenesis of drug-induced idiosyncratic liver injury (DILI) is that parent compounds are rendered hepatotoxic by metabolism, mainly by cytochrome (CYP) 450, although other metabolic pathways can contribute. Anecdotal reports suggest a role of CYP 450 polymorphisms in DILI. We aimed to assess in a series of Spanish DILI patients the prevalence of important allelic variants of CYP2C9 and CYP2C19, known to be involved in the metabolism of several hepatotoxic drugs.

EXPERIMENTAL APPROACH

Genotyping of CYP2C9 ((*)2, (*)3) and CYP2C19 ((*)2 and (*)3), was carried out in a total of 28 and 32 patients with a well established diagnosis of DILI. CYP2C9 and CYP2C19 variants were analysed in genomic DNA by means of PCR-FRET and compared with previous findings in other Caucasian populations.

KEY RESULTS

CYP2C9 and CYP2C19 allele and genotype frequencies were in agreement with Hardy-Weinberg equilibrium. Fourteen patients (50%) were heterozygous and 1(4%) found to be compound heterozygous for the CYP2C9 allele. Seven (22%) were found to carry one and 1(3%) carried two CYP2C19 mutated alleles. No patients were homozygous for (*)3 allele. The distribution of both CYP2C9 and CYP2C19 allelic variants in DILI patients were similar to those in other Caucasian populations. Patients with variant and those with wild-type alleles did not differ in regard to clinical presentation of DILI, type of injury and outcome.

CONCLUSIONS AND IMPLICATIONS

We find no evidence to support CYP2C9 and CYP2C19 genetic polymorphisms as predictable potential risk factors for DILI.

[Genetic background of multifactorial liver and bile duct diseases]

The majority of liver diseases, are complex. They are the results of interactions between several genes and environmental factors. Familial aggregation and higher concordance rate of monozygotic twins compared to those of dizygotic twins provide evidence for the importance of genetic factors in the pathogenesis. There are only limited data in connection with the genetic background of multifactorial liver diseases. In the future, the genetic background may permit prevention, early, accurate diagnosis, prediction of disease course, complications, prognosis, as well as treatment response.

Incidence of statin hepatotoxicity in patients with hepatitis C

BACKGROUND AND AIMS

Statins are considered contraindicated in patients with chronic liver disease. Our objective was to determine the risk of developing hepatotoxicity from statin therapy in hyperlipidemic patients with hepatitis C.

METHODS

Changes in liver biochemistry values within 12 months compared with baseline were determined in 3 cohorts matched for age, sex, and body mass index: (I) 166 anti-hepatitis C virus (HCV)-positive hyperlipidemic veterans who were initiated on statin therapy; (II) 332 anti-HCV-positive veterans who had not received statin therapy; and (III) 332 anti-HCV-negative hyperlipidemic veterans who were initiated on statin therapy. An increase in liver biochemistry values was defined as mild-moderate or severe as proposed in a previous study on statin hepatotoxicity in a non-hepatitis C population.

RESULTS

In patients with hepatitis C, statin therapy (cohort I) was associated with a higher incidence of mild-moderate liver biochemistry value increases compared with those not on statin therapy (cohort II) (22.9% vs 13.3%, respectively, P = .009), but a lower incidence of severe increases (1.2% vs 6.6%, respectively, P = .015). Among patients started on statin therapy (cohorts I and III), the incidence of mild-moderate liver biochemistry value increases (22.9% vs 16.3%, respectively, P = .094), severe increases (1.2% vs 1%, respectively, P = .874), or discontinuation of statin therapy as a result of hepatotoxicity (21.6% vs 9.2%, respectively, P = .147) were similar in hepatitis C-positive and hepatitis C-negative patients.

CONCLUSIONS

Statin therapy was not associated with a higher risk of severe hepatotoxicity in patients with chronic hepatitis C and appeared safe.

Metabolism and transport of oxazaphosphorines and the clinical implications

The oxazaphosphorines including cyclophosphamide (CPA), ifosfamide (IFO), and trofosfamide represent an important group of therapeutic agents due to their substantial antitumor and immuno-modulating activity. CPA is widely used as an anticancer drug, an immunosuppressant, and for the mobilization of hematopoetic progenitor cells from the bone marrow into peripheral blood prior to bone marrow transplantation for aplastic anemia, leukemia, and other malignancies. New oxazaphosphorines derivatives have been developed in an attempt to improve selectivity and response with reduced toxicity. These derivatives include mafosfamide (NSC 345842), glufosfamide (D19575, beta-D-glucosylisophosphoramide mustard), NSC 612567 (aldophosphamide perhydrothiazine), and NSC 613060 (aldophosphamide thiazolidine). This review highlights the metabolism and transport of these oxazaphosphorines (mainly CPA and IFO, as these two oxazaphosphorine drugs are the most widely used alkylating agents) and the clinical implications. Both CPA and IFO are prodrugs that require activation by hepatic cytochrome P450 (CYP)-catalyzed 4-hydroxylation, yielding cytotoxic nitrogen mustards capable of reacting with DNA molecules to form crosslinks and lead to cell apoptosis and/or necrosis. Such prodrug activation can be enhanced within tumor cells by the CYP-based gene directed-enzyme prodrug therapy (GDEPT) approach. However, those newly synthesized oxazaphosphorine derivatives such as glufosfamide, NSC 612567 and NSC 613060, do not need hepatic activation. They are activated through other enzymatic and/or non-enzymatic pathways. For example, both NSC 612567 and NSC 613060 can be activated by plain phosphodiesterase (PDEs) in plasma and other tissues or by the high-affinity nuclear 3'-5' exonucleases associated with DNA polymerases, such as DNA polymerases and epsilon. The alternative CYP-catalyzed inactivation pathway by N-dechloroethylation generates the neurotoxic and nephrotoxic byproduct chloroacetaldehyde (CAA). Various aldehyde dehydrogenases (ALDHs) and glutathione S-transferases (GSTs) are involved in the detoxification of oxazaphosphorine metabolites. The metabolism of oxazaphosphorines is auto-inducible, with the activation of the orphan nuclear receptor pregnane X receptor (PXR) being the major mechanism. Oxazaphosphorine metabolism is affected by a number of factors associated with the drugs (e.g., dosage, route of administration, chirality, and drug combination) and patients (e.g., age, gender, renal and hepatic function). Several drug transporters, such as breast cancer resistance protein (BCRP), multidrug resistance associated proteins (MRP1, MRP2, and MRP4) are involved in the active uptake and efflux of parental oxazaphosphorines, their cytotoxic mustards and conjugates in hepatocytes and tumor cells. Oxazaphosphorine metabolism and transport have a major impact on pharmacokinetic variability, pharmacokinetic-pharmacodynamic relationship, toxicity, resistance, and drug interactions since the drug-metabolizing enzymes and drug transporters involved are key determinants of the pharmacokinetics and pharmacodynamics of oxazaphosphorines. A better understanding of the factors that affect the metabolism and transport of oxazaphosphorines is important for their optional use in cancer chemotherapy.

Drug bioactivation, covalent binding to target proteins and toxicity relevance

A number of therapeutic drugs with different structures and mechanisms of action have been reported to undergo metabolic activation by Phase I or Phase II drug-metabolizing enzymes. The bioactivation gives rise to reactive metabolites/intermediates, which readily confer covalent binding to various target proteins by nucleophilic substitution and/or Schiff's base mechanism. These drugs include analgesics (e.g., acetaminophen), antibacterial agents (e.g., sulfonamides and macrolide antibiotics), anticancer drugs (e.g., irinotecan), antiepileptic drugs (e.g., carbamazepine), anti-HIV agents (e.g., ritonavir), antipsychotics (e.g., clozapine), cardiovascular drugs (e.g., procainamide and hydralazine), immunosupressants (e.g., cyclosporine A), inhalational anesthetics (e.g., halothane), nonsteroidal anti-inflammatory drugs (NSAIDSs) (e.g., diclofenac), and steroids and their receptor modulators (e.g., estrogens and tamoxifen). Some herbal and dietary constituents are also bioactivated to reactive metabolites capable of binding covalently and inactivating cytochrome P450s (CYPs). A number of important target proteins of drugs have been identified by mass spectrometric techniques and proteomic approaches. The covalent binding and formation of drug-protein adducts are generally considered to be related to drug toxicity, and selective protein covalent binding by drug metabolites may lead to selective organ toxicity. However, the mechanisms involved in the protein adduct-induced toxicity are largely undefined, although it has been suggested that drug-protein adducts may cause toxicity either through impairing physiological functions of the modified proteins or through immune-mediated mechanisms. In addition, mechanism-based inhibition of CYPs may result in toxic drug-drug interactions. The clinical consequences of drug bioactivation and covalent binding to proteins are unpredictable, depending on many factors that are associated with the administered drugs and patients. Further studies using proteomic and genomic approaches with high throughput capacity are needed to identify the protein targets of reactive drug metabolites, and to elucidate the structure-activity relationships of drug's covalent binding to proteins and their clinical outcomes.

Pathophysiology of cholangiopathies

The diseases of the intrahepatic biliary tree are a large group of potentially evolutive congenital and acquired liver disorders affecting both the adult and pediatric populations. They represent a relevant cause of liver-related morbidity and mortality and an important indication for liver transplantation, particularly in children. While the practical approach to patients affected by biliary tree diseases has not significantly changed yet, the conceptual approach to the pathophysiology of cholangiopathies has witnessed important advances that will be discussed. The primary cell target of the pathogenetic sequence of these disorders is the biliary epithelium. Cholangiocytes have multifaceted functions, not limited to bile production. Their capability to secrete a range of different pro-inflammatory mediators, cytokines, and chemokines indicates a major role of cholangiocytes in the inflammatory reaction. Furthermore, paracrine secretion of growth factors and peptides mediates an extensive cross-talk with other liver cell types, including hepatocytes, stellate, and endothelial and inflammatory cells. Cholangiopathies share a number of pathogenetic mechanisms, including inflammation, cholestasis, fibrosis, apoptosis, altered development, and neoplastic transformation. These basic disease mechanisms will be discussed in detail, along with the distinct features of a number of cholangiopathies. Furthermore, an increase in the biliary cell compartment is a common response to many forms of liver injury, from cholangiopathies to viral and fulminant hepatitis. Elucidation of these pathophysiologic mechanisms will likely provide clues for future therapeutic strategies. Furthermore, understanding the role of cholangiocytes in liver regeneration/repair and the mechanisms of cholangiocyte activation and their relationship with liver progenitor cell will be of further interest.

Drug metabolism by cultured human hepatocytes: how far are we from the in vivo reality?

The investigation of metabolism is an important milestone in the course of drug development. Drug metabolism is a determinant of drug pharmacokinetics variability in human beings. Fundamental to this are phenotypic differences, as well as genotypic differences, in the expression of the enzymes involved in drug metabolism. Genotypic variability is easy to identify by means of polymerase chain reaction-based or DNA chip-based methods, whereas phenotypic variability requires direct measurement of enzyme activities in liver, or, indirectly, measurement of the rate of metabolism of a given compound in vivo. There is a great deal of phenotypic variability in human beings, only a minor part being attributable to gene polymorphisms. Thus, enzyme activity measurements in a series of human livers, as well as in vivo studies with human volunteers, show that phenotypic variability is, by far, much greater than genotypic variability. In vitro models are currently used to investigate the hepatic metabolism of new compounds. Cultured human hepatocytes are considered to be the closest model to the human liver. However, the fact that hepatocytes are placed in a microenvironment that differs from that of the cells in the liver raises the question of to what extent drug metabolism variability observed in vitro actually reflects that in the liver in vivo. This issue has been examined by investigating the metabolism of the model compound, aceclofenac (an approved analgesic/anti-inflammatory drug), both in vitro and in vivo. Hepatocytes isolated from programmed liver biopsies were incubated with aceclofenac, and the metabolites formed were investigated by HPLC. The patients were given the drug during the course of clinical recovery, and the metabolites, largely present in urine, were analysed. In vitro and in vivo data from the same individual were compared. There was a good correlation between the in vitro and in vivo relative abundance of oxidised metabolites (4'-OH-aceclofenac + 4'-OH-diclofenac; Spearman's rho = 0.855), and the hydrolysis of aceclofenac (diclofenac + 4'-OH-aceclofenac + 4'-OH-diclofenac; rho = 0.691), while the conjugation of the drug in vitro was somewhat lower than in vivo. Globally, the metabolism of aceclofenac in vitro correlated with the amount of metabolites excreted in urine after 16 hours (rho = 0.95). Overall, although differing among assays, the in vitro/in vivo metabolism data for each patient were surprisingly similar. Thus, the variability observed in vitro appears to reflect genuine phenotypic variability among the donors.

Comparison of three commercially available assays for HCV RNA using the international unit standard: implications for management of patients with chronic hepatitis C virus infection in clinical practice

OBJECTIVES

The present study was performed to evaluate the impact of the international unit standard for measuring HCV RNA in the management of patients with chronic hepatitis C virus (HCV) infection.

METHODS

The three assays used were Amplicor Monitor PCR, the National Genetics Institute PCR assay, and branched chain DNA. HCV RNA was measured at four time points (baseline, 3 months after the start of therapy, at the end of treatment, and 6 months after discontinuation of therapy) in 106 consecutive patients who received interferon and ribavirin for chronic HCV.

RESULTS

The mean age of the patients was 44 yr. Of the patients, 62% were male, 24% were African American, 38% had bridging fibrosis or cirrhosis, and 75% were HCV genotype 1. Of the 424 samples analyzed, 82-89% of values were within 1 log unit and 85-92% were within 2 log units by the various assays. This variability was not dependent upon HCV genotype. HCV RNA was undetectable in 1.4-6.8% of samples when virus was detected by another assay. The mean HCV RNA in these discordant samples was 1.47-6.33 log IU/ml (30-2,100,000 IU/ml).

CONCLUSIONS

These data demonstrate that approximately 90% of serum values for HCV RNA were within 1 log unit by the international unit standard regardless of which virological assay was used. However, false positive and false negative results as well as variations in the HCV RNA level of more than 1 to 2 log units can occur with any of the assays, and these results may have an impact upon the management of patients receiving interferon therapy. It is therefore unwise in clinical practice to base important treatment decisions upon a single HCV RNA determination.

Leukotriene antagonists

Hepatotoxicity is the most common cause of fulminant hepatic failure in the United States and the main indication for market withdrawal of drugs. This condition has been increasingly recognized as a problem of enormous medical, financial legal, and regulatory importance. It is in context of this heightened awareness of hepatotoxicity, particularly associated with new high profile drugs, that the authors reviews the published data regarding liver injury related to a novel group of asthma drugs.

Carbamazepine-provoked hepatotoxicity and possible aetiopathological role of glutathione in the events. Retrospective review of old data and call for new investigation

The antiepileptic drug (AED) carbamazepine is widely used in the treatment of different kinds of seizures as well as affective and behavioural disorders. This paper presents an epidemiological study of carbamazepine-induced hepatic injuries and death, and describes the possible mechanisms of its toxicity. A retrospective analysis of clinical data revealed that the likelihood of hepatic death was comparatively higher in children, particularly when they were receiving medication with multiple AEDs, whereas reversible hepatic injuries were more likely to be seen in elderly patients. As suggested in this paper, the development of carbamazepine hepatotoxicity is rare, and unpredictable with the present state of knowledge, but it is somehow related to disturbance of glutathione metabolism, although data in this regard are imperfect. There appear to be two types of carbamazepine-initiated idiosyncratic liver injury, hypersensitivity and toxin-induced. It is feasible that both are due to the accumulation of toxic metabolite(s), and arene oxides may probably be considered as damaging derivatives of carbamazepine metabolism. Despite the lack of clear-cut underlying clinical and experimental findings in those patients in whom an inherited weakness of drug eliminating capacity is present, those conditions that may deteriorate glutathione balance, may increase the possibility of the emergence of toxic events during carbamazepine therapy. Finally, some recommendations for carbamazepine therapy are presented.

Phenytoin-induced toxic cholestatic hepatitis in a patient with skin lesions: case report

Phenytoin is a highly effective and widely prescribed anticonvulsant agent, but it can be associated with dose-related side effects and hypersensitivity reactions. We present a case of phenytoin-induced cholestatic hepatotoxicity in a 47-year-old woman who had exfoliative dermatitis, an increase in liver enzymes with a cholestatic pattern, and eosinophilia after 25 days of phenytoin therapy. The diagnostic workup showed no other possible causes, and the results of a percutaneous liver biopsy were consistent with drug-induced toxic hepatitis. Within 3 weeks after discontinuing phenytoin therapy, her liver function tests returned to normal values.

A review of the common properties of drugs with idiosyncratic hepatotoxicity and the "multiple determinant hypothesis" for the manifestation of idiosyncratic drug toxicity

Idiosyncratic drug toxicity is generally believed to be a phenomenon that cannot be readily evaluated experimentally. Reasons for this difficulty include the following: 1. It is a rare event (<1/5,000) and therefore impossible to be studied in clinical trials; 2. It is a human-specific event not detectable in experimental animals. To aid the understanding of idiosyncratic toxicity and to develop an experimental strategy for this phenomenon, a hypothesis is proposed. The hypothesis states that the low frequency of idiosyncratic drug toxicity is due to the requirements for the occurrence of multiple critical and discrete events, with the probability for the occurrence of idiosyncratic drug toxicity as a product of the probabilities of each event. The key determinants of these critical events are proposed to be: 1. Chemical properties; 2. exposure; 3. environmental factors; and 4. genetic factors. Based on this hypothesis, idiosyncratic drug toxicity can be evaluated experimentally via studying these key determinants. The chemical properties critical to idiosyncratic drug toxicity are identified via a review of the common properties of drugs that cause idiosyncratic liver toxicity. These properties include: 1. Formation of reactive metabolites. 2. Metabolism by P450 isoforms. 3. Preponderance of P450 inducers, and 4. Occurrence of clinically significant pharmacokinetic interactions with co-administered drugs. Based on this review, it is proposed that these common properties may be useful experimental endpoints for the prediction and therefore avoidance of the selection of drug candidates with idiosyncratic drug toxicity for further development.

Use of complementary and alternative medicine in patients with liver disease

OBJECTIVES

Complementary and alternative medicine (CAM) is used by 42% of the U.S. population. Its use among patients with chronic liver disease has not been well defined. Toward that end, we surveyed patients in six geographically diverse liver disease clinics in the United States for use of CAM.

METHODS

Patients attending six liver disease clinics were polled via a common questionnaire regarding their use of CAM. Demographic information was obtained to identify predictors of CAM use. Statistical analysis included univariate and multivariate analysis using logistic regression.

RESULTS

A total of 989 patients completed the questionnaire. Of these, 389 (39%) admitted to using some form of CAM at least once during the preceding month; 21% admitted to using herbal preparations, and 13% used herbs to treat their liver disease. Five variables were found to be predictive of alternative therapy use: female sex, young age, level of education, annual income, and geographic location. In all, 74% of patients reported using CAM in addition to the medications prescribed by their physician, but 26% did not inform their physician of their CAM use.

CONCLUSIONS

CAM use is as common among patients visiting liver disease clinics in the United States as in the general population (39% vs 42%). Many patients are using herbs to treat their liver disease but are declining to discuss this use with their physician.

Immune-mediated drug-induced liver disease

Drug-induced immune-mediated hepatic injury is an adverse immune response against the liver that results in a disease with hepatitic, cholestatic, or mixed clinical features. Drugs such as halothane, tienilic acid, dihydralazine, and anticonvulsants trigger a hepatitic reaction, and drugs such as chlorpromazine, erythromycins, amoxicillin-calvulanic acid, sulfonamides and sulindac trigger a cholestatic or mixed reaction. Unstable metabolites derived from the metabolism of the drug may bind to cellular proteins or macromolecules, leading to a direct toxic effect on hepatocytes. Protein adducts formed in the metabolism of the drug may be recognized by the immune system as neoantigens. Immunocyte activation may then generate autoantibodies and cell-mediated immune responses, which in turn damage the hepatocytes. Cytochromes 450 are the major oxidative catalysts in drug metabolism, and they can form a neoantigen by covalently binding with the drug metabolite that they produce. Autoantibodies that develop are selectively directed against the particular cytochrome isoenzyme that metabolized the parent drug. The hapten hypothesis proposes that the drug metabolite can act as a hapten and can modify the self of the individual by covalently binding to proteins. The danger hypothesis proposes that the immune system only responds to a foreign antigen if the antigen is associated with a danger signal, such as cell stress or cell death. Most clinically overt adverse hepatic events associated with drugs are unpredictable, and they have intermediate (1 to 8 weeks) or long latency (up to 12 months) periods characteristic of hypersensitivity reactions. Immune-mediated drug-induced liver disease nearly always disappears or becomes quiescent when the drug is removed. Methyldopa, minocycline, and nitrofurantoin can produce a chronic hepatitis resembling AIH if the drug is continued.

Neonatal cholestatic hepatitis from carbamazepine exposure during pregnancy and breast feeding

OBJECTIVE

To report a case of transient cholestatic hepatitis occurring in an infant between the third and seventh weeks of life, most likely due to carbamazepine exposure during pregnancy and breast feeding.

CASE SUMMARY

A boy, born to an epileptic mother who had been treated with carbamazepine monotherapy throughout pregnancy and breast feeding, experienced asphyxia at birth with transient hepatic dysfunction in the first week of life. After full recovery from asphyxia, he experienced a second period of liver dysfunction, presenting as cholestatic hepatitis that lasted approximately 5 weeks. Infectious and metabolic etiologies as well as extrahepatic biliary atresia were excluded.

DISCUSSION

Carbamazepine is known to induce hepatic damage in children and adults. As the drug crosses the placenta and is excreted into breast milk, infants of mothers taking carbamazepine might also develop liver dysfunction. In addition to the present case, there are 2 well-documented case reports of cholestasis in association with transplacental and transmammary carbamazepine exposure.

CONCLUSIONS

Carbamazepine-induced hepatitis may occur in association with prenatal exposure and breast feeding. This may expose infants to unnecessary diagnostic procedures, and should therefore be mentioned in the company's product information.

Task force report: future research needs for the prevention and management of immune-mediated drug hypersensitivity reactions

Immune-mediated drug hypersensitivity reactions (IDHR) have a significant impact on clinical practice, drug development, and public health. However, research to understand IDHR mechanisms and to develop diagnostic and predictive tests has been limited. To stimulate more research, a task force with representatives from the key stakeholders (research clinicians, regulatory scientists, and immunotoxicologists from the pharmaceutical industry) was assembled to identify critical data gaps and opportunities and to make recommendations on how to overcome some of the barriers to IDHR research and address research needs. It is hoped that this report will act as a springboard for future discussions and progress toward increased funding and development of organizational structures for IDHR research.

Identification of a reactive metabolite of terbinafine: insights into terbinafine-induced hepatotoxicity

Oral terbinafine treatment for superficial fungal infections of toe and fingernails is associated with a low incidence (1:45000) of hepatobiliary dysfunction. Due to the rare and unpredictable nature of this adverse drug reaction, the mechanism of toxicity has been hypothesized to be either an uncommon immunological or metabolically mediated effect. However, there is little evidence to support either mechanism, and toxic metabolites of terbinafine have not been identified. We incubated terbinafine with both rat and human liver microsomal protein in the presence of GSH and were able to trap an allylic aldehyde, 7,7-dimethylhept-2-ene-4-ynal (TBF-A), which corresponds to the N-dealkylation product of terbinafine. TBF-A was also prepared synthetically and reacted with excess GSH to yield conjugates with HPLC retention times and mass spectra identical to those generated in the microsomal incubations. The major GSH conjugate, characterized by (1)H NMR, corresponds to addition of GSH in a 1,6-Michael fashion. There remains a second electrophilic site on this metabolite, which can bind either to a second molecule of GSH or to cellular proteins via a 1,4-Michael addition mechanism. Moreover, we demonstrated that the formation of the GSH conjugates was reversible. We speculate that this allylic aldehyde metabolite, formed by liver enzymes and conjugated with GSH, would be transported across the canalicular membrane of hepatocytes and concentrated in the bile. The mono-GSH conjugate, which is still reactive, could bind to hepatobiliary proteins and lead to direct toxicity. Alternatively, it could modify canalicular proteins and lead to an immune-mediated reaction causing cholestatic dysfunction.

Drug biotransformation by human hepatocytes. In vitro/in vivo metabolism by cells from the same donor

BACKGROUND/AIMS

Cultured human hepatocytes are considered a close model to human liver. However, the fact that hepatocytes are placed in a microenvironment that differs from that of the cell in the liver raises the question: to what extent does drug metabolism in vitro reflect that of the liver in vivo? This issue was examined by investigating the in vitro and in vivo metabolism of aceclofenac, an analgesic/anti-inflammatory drug.

METHODS

Hepatocytes isolated from programmed liver biopsies were incubated with aceclofenac, and the metabolites formed were investigated by HPLC. During the course of clinical recovery, patients were given the drug, and the metabolites, largely present in the urine, were analyzed. In vitro and in vivo data of the same individual were compared.

RESULTS

The relative abundance of oxidized metabolites in vitro (i.e. 4'OH-aceclofenac + 4'OH-diclofenac vs. total hydroxylated metabolites; Spearman's p = 0.855), as well the hydrolysis of aceclofenac (4'OH-diclofenac vs. 4'OH-aceclofenac + 4'OH-diclofenac; p = 0.691) correlated well with in vivo data. The conjugation of the drug in vitro (24.6 +/- 7.6%) was lower than that in vivo (44.9 +/- 5.3%). The rate of 4'OH-aceclofenac formation in vitro correlated with the amount of metabolites excreted in urine after 16 h (p = 0.95).

CONCLUSIONS

The in vitro/in vivo metabolism of the drug was surprisingly similar in each patient. The variability observed in vitro reflected an existing phenotypic variability among donors.