IsonaRif and Hepatotoxicity

The use of isoniazid is contraindicated in patients with acute liver disease or a history of hepatic injury due to isoniazid. Caution is advised when using the drug in patients with chronic liver disease or a history of alcoholism. Isoniazid has been associated with severe and sometimes fatal hepatitis, which may occur even after many months of therapy. In a US Public Health Service Surveillance Study of nearly 14,000 isoniazid patients, the incidence of hepatitis was 1.25%, of which 4.6% was fatal. However, more recent studies have reported considerably lower rates when CDC guidelines for selection and monitoring of patients were followed. Epidemiologic studies indicate an increased incidence with increasing age, alcohol use, and female gender. As a precautionary measure, routine monitoring of serum transaminases (SGOT, SGPT) and bilirubin may be considered, although a transient and harmless increase in serum transaminase reportedly occurs in 10% to 20% of patients, usually in the first 3 months of therapy. Patients should be advised to promptly discontinue isoniazid therapy and seek medical attention if they experience signs or symptoms suggestive of liver damage such as fever, rash, anorexia, nausea, vomiting, fatigue, right upper quadrant pain, dark urine, and jaundice. Reinstitution of the drug should occur only after symptoms and laboratory abnormalities resolve, with low and gradually increasing dosages.

The use of rifampin has been associated with hepatocellular injury and liver dysfunction. Hepatitis and jaundice resulting in death have occurred, mostly in patients with underlying liver disease and during coadministration with other hepatotoxic agents including other antituberculous drugs such as isoniazid and pyrazinamide. Therapy with rifampin should be administered cautiously and under strict medical supervision in patients with liver disease or a history of alcoholism. Serum transaminases (ALT, AST) and bilirubin should be measured at baseline and every 2 to 4 weeks during therapy, but keeping in mind that elevated levels may occur transiently in 10% to 15% of patients, usually during the early days of treatment. Patients should be instructed to discontinue the drug promptly and seek medical attention if signs and symptoms of hepatic injury develop, including fever, rash, anorexia, nausea, vomiting, fatigue, right upper quadrant pain, dark urine, and jaundice.