Causality assessment versus guilt-by-association in drug hepatotoxicity

The rational use of potentially hepatotoxic medications in patients with underlying liver disease

Given the fact that as many as 9% of all adverse drug reactions involve toxic effects on the liver and with upwards of 50% of all cases of fulminant hepatic failure being ascribed to acetaminophen and other agents, the safe use of medications takes on an even greater importance whenever the prescription of potentially hepatotoxic drugs to patients with underlying liver disease is considered. In general, it is thought that most drugs can be safely administered in the setting of liver disease without an increased risk of hepatotoxicity, although the evidence on which this statement is based often relies more on clinical judgement than on clinical studies. Several drugs appear to have an increased risk of hepatotoxicity in patients with underlying liver disease based on either clinical reports or extrapolated pharmacological data. These agents, including methotrexate, niacin and the antiretroviral and antituberculosis drugs, carry warnings about their use in patients with a variety of liver conditions. The data supporting the hepatotoxic risk of scores of additional drugs, such as the 3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors ("statins"), the newer thiazolidinediones (rosiglitazone, pioglitazone), and tamoxifen, among others, in patients with liver disease are generally lacking by evidence-based studies. However, clinical and biochemical monitoring is routinely recommended or required, often to make up for the lack of information on the true risk of clinically significant liver toxicity of these agents in individuals both with and without underlying liver disease. This article will review what is and what is not known about prescribing in the setting of acute and chronic liver disease and offers recommendations to help promote the safe and rational use of potentially hepatotoxic medications in these patients.

Progressive cholestatic liver disease associated with clarithromycin treatment

The authors report a case of an acute toxic cholestatic reaction to clarithromycin, proven by liver biopsy, in a patient with comorbid diseases, prior exposure to erythromycin and ultimate death. No autopsy was performed. A 59-year-old woman with diabetes mellitus and chronic renal insufficiency received clarithromycin 500 mg twice daily for 3 days for acute maxillary sinusitis and then developed a rash and jaundice. She was hospitalized 11 days after stopping clarithromycin. Progressive cholestatic jaundice accompanied by oligo-anuric renal failure requiring hemodialysis ensued. Liver biopsy showed pure bilirubinostasis without parenchymal inflammation. On the 22nd hospital day, after clinical deterioration, she died from an apparent cardiopulmonary death. This is the first report in the literature of a fatality associated with a short-term, low (1 g) daily dose of drug-induced pure cholestasis, an entity not previously identified with severe drug-induced hepatotoxicity.

Drug-induced liver disease

Although the year 2001 did not see any prescription drugs withdrawn because of drug-induced liver disease, the US Food and Drug Administration requested that dietary supplements containing comfrey be taken off the market because of the danger of hepatic injury. The Food and Drug Administration remains very involved in the process by which drug-induced liver disease can be detected early in drug development and in the determination of how best to prevent hepatotoxicity after drug approval. A workshop on drug-induced liver disease cosponsored by the Food and Drug Administration, the Pharmaceutical Research and Manufacturers Association, and the American Association for the Study of Liver Diseases was held in Washington, DC, in February 2001, and the resulting white paper outlined several areas for research. A number of agents were newly described as causing various forms of liver injury, and several others had drug-induced liver disease confirmed by additional reports. Several investigators dealt with the difficulties inherent in establishing causality of drug-induced liver disease and the potential negative consequences of wrongly attributing hepatotoxicity to a particular agent. In one recent series, more than half the instances of alleged drug-induced liver disease were found to have other causes, often leading to a delay in the actual diagnosis and appropriate management. Case reports in particular were often misleading. Although several drug assessment scales have been developed, none appears to be foolproof.

Drug-induced liver disorders: implications for drug development and regulation

Drug-induced hepatotoxicity is a frequent cause of liver disease. Although often presenting as acute hepatitis and/or cholestasis, virtually any clinical-pathological pattern of acute or chronic liver disease can occur. Most reactions occur in a small proportion of the population using a particular drug. Each drug associated with hepatotoxicity tends to have a characteristic signature regarding latency and pattern of injury. The mechanism can be drug metabolism-dependent or related to the chemical properties of the parent drug. The former are immune mediated or due to metabolic idiosyncrasy. Monitoring serum ALT levels is of unproven effectiveness but should be considered when there is an increased risk of delayed onset serious hepatitis-like reactions. The key for the future is improved identification of toxic potential in preclinical studies, clinical trials and postmarketing experience. The elucidation of the genetic and environmental mechanisms contributing to delayed idiosyncratic reactions is a major barrier to overcome in this field.

Expression profiling of acetaminophen liver toxicity in mice using microarray technology

Drug-induced hepatotoxicity causes significant morbidity and mortality and is a major concern in drug development. This is due, in large part, to insufficient knowledge of the mechanism(s) of drug-induced liver injury. In order to address this problem, we have evaluated the modulation of gene expression within the livers of mice treated with a hepatotoxic dose of acetaminophen (APAP) using high-density oligonucleotide microarrays capable of determining the expression profile of >11,000 genes and expressed sequence tags (ESTs). Significant alterations in gene expression, both positive and negative, were noted within the livers of APAP-treated mice. APAP-induced toxicity affected numerous aspects of liver physiology causing, for instance, >twofold increased expression of genes that encode for growth arrest and cell cycle regulatory proteins, stress-induced proteins, the transcription factor LRG-21, suppressor of cytokine signaling (SOCS)-2-protein, and plasminogen activator inhibitor-1 (PAI-1). A number of these and other genes and ESTs were detectable within the liver only after APAP treatment suggesting their potential importance in propagating or preventing further toxicity. These data provide new directions for mechanistic studies that may lead to a better understanding of the molecular basis of drug-induced liver injury and, ultimately, to a more rational design of safer drugs.