PDP-Isoniazid Warnings

Severe and sometimes fatal hepatitis associated with isoniazid therapy may occur and may develop even after months of treatment. Serum AST levels become elevated in about 10 to 20% of patients, usually during the first few months of therapy, but it can occur at any time. Usually enzyme levels return to normal despite continuance of the drug, but in some cases progressive liver dysfunction occurs. The risk of developing hepatitis is increased with pre-existing liver disease, increasing age, concurrent use of other hepatotoxic medications and excessive or chronic use of alcohol. Patients given isoniazid should be carefully monitored and interviewed regularly. Patients should be instructed to report immediately any of the prodomal symptoms of hepatitis, such as fatigue, weakness, malaise, anorexia, nausea or vomiting. If symptoms and signs suggestive of hepatic damage are detected, discontinue the drug promptly and follow the patient closely. An alternative agent should be used since continued use of isoniazid in these patients may cause a more severe form of liver damage. Defer preventive treatment in individuals with acute hepatic diseases. If isoniazid must be reinstituted, this should be done only after symptoms and laboratory abnormalities have cleared. Restart in very small and gradually increasing doses, and withdraw immediately if there is any indication of recurrent liver involvement.
Susceptibility/Resistance: Development of Drug Resistant Bacteria: Prescribing pdp-ISONIAZID in the absence of a proven or strongly suspected bacterial infection is unlikely to provide benefit to the patient and risks the development of drug-resistant bacteria.