Drug-induced hepatotoxicity

Cysteine/Glutathione Deficiency: A Significant and Treatable Corollary of Disease

Glutathione (GSH) deficiency may play a pivotal role in a variety of apparently unrelated clinical conditions and diseases. Orally administered N-acetylcysteine (NAC), which replenishes the cysteine required for GSH synthesis, has been tested in a large number of randomized placebo-controlled trials involving these diseases and conditions. This chapter focused on developing a base of evidence suggesting that NAC administration improves disease by increasing cysteine and/or GSH in a variety of diseases, thereby implying a significant role for GSH deficiency in the clinical basis of many diseases. To develop this base of evidence, we systematically selected studies which considered the hypothesis that the therapeutic efficacy for NAC is an indication that cysteine and/or GSH deficiency is a pathophysiological part of the diseases studied. In this manner we focus this chapter on explaining the biological mechanisms of NAC therapy in a wide variety of disorders and demonstrate its ubiquitous role in improving disease that involves disrupted GSH and/or cysteine metabolism.

Isoflurane hepatitis-induced liver failure: a case report

A case of fulminant hepatic failure two days following an uneventful operation during isoflurane anesthesia is presented. Investigations included elevated bilirubin and serum transaminases in the absence of any other cause of hepatic dysfunction. The patient died on the fourth postoperative day. Subsequent postmortem examination showed centrilobular coagulative necrosis consistent with drug toxicity, with isoflurane as the most likely toxic agent.

Drug-induced cholestasis

Drug-induced cholestasis is a common entity, seen with numerous classes of pharmacological agents. A high index of suspicion is required for the correct diagnosis. Different clinical syndromes may be recognized, with variable degrees of hepatitis in association with cholestasis. The most important aspect of treatment is prompt discontinuation of the offending drug. Several agents have been used for symptomatic relieve of the pruritus associated with cholestasis, including cholestyramine, ursodeoxycholic acid, and opiate antagonists, with limited results. Prognosis is usually good, with few cases of prolonged cholestasis leading to vanishing bile duct syndrome. Liver failure may rarely occur if diagnosis goes unrecognized and the inciting drug is not withdrawn.

S-adenosyl-L-methionine (SAMe) for the treatment of acetaminophen toxicity in a dog

An 8-month-old, spayed female Shetland sheepdog presented 48 hours after ingesting acetaminophen (1 gm/kg body weight). On presentation, the dog was laterally recumbent and hypovolemic. The dog had brown mucous membranes, severe Heinz-body hemolytic anemia, bleeding tendencies, and a red blood cell (RBC) glutathione (GSH) concentration that was 10% of reference values, despite a regenerative erythroid response. Treatment with s-adenosyl-l-methionine (SAMe) as a GSH donor successfully rescued this dog, despite the animal's late presentation after drug ingestion. A loading dose (40 mg/kg body weight) of a stable SAMe salt per os was followed by a maintenance dose (20 mg/kg body weight) sid for 7 days. Additional therapeutic interventions included an intravenous (i.v.) infusion of one unit of packed RBCs (on admission), i.v. fluid support (3 days), and famotidine (7 days) to reduce gastric acidity. Sequential assessment of RBC GSH concentrations and RBC morphology documented response to antidote administration within 72 hours. This case suggests that SAMe may provide a therapeutic option for treatment of acetaminophen toxicosis in dogs capable of retaining an orally administered antidote and maintaining adequate hepatic function for metabolism of SAMe to its thiol substrates.

Alcohol-acetaminophen syndrome. Even moderate social drinkers are at risk

In long-term alcohol users, the syndrome of hepatotoxicity from acetaminophen taken in therapeutic or modestly excessive doses is distinctive. It is characterized by striking elevation of transaminase levels and the potential for acute liver failure with high morbidity and mortality rates. A high index of suspicion should be maintained; in any patient with evidence of acute hepatic injury, a complete history of over-the-counter drug use should be obtained and acetaminophen levels checked. If there is doubt about the dose or time of ingestion, one should err on the side of treatment with acetylcysteine, because it is both effective and safe. Therapy should be initiated as early as possible, but even late administration may be of benefit. Timely contact with a medical center that has liver transplantation capabilities should be made before encephalopathy becomes advanced. Heightened awareness of this preventable and treatable condition is needed by healthcare providers and acetaminophen users alike. Because the minimum safe dose of acetaminophen is not known in the setting of chronic alcohol use, it seems prudent in such situations to avoid acetaminophen altogether, especially during brief periods of abstinence.