Drugs A - Z

isoniazid Images

Generic Name: isoniazid

Brand Names: Nydrazid

There is an FDA Alert for this drug. Click here to view it.

  • Severe and sometimes fatal hepatitis reported; hepatitis usually develops during the first 3 months of therapy but may develop after many months.
  • Risk of developing hepatitis is age related. Approximate case rates by age are: <1 per 1000 in individuals <20 years of age; 3 per 1000 in individuals 20–34 years of age; 12 per 1000 in individuals 35–49 years of age; 23 per 1000 in individuals 50–64 years of age; 8 per 1000 in individuals >65 years of age.
  • Risk of hepatitis is increased by daily consumption of alcohol, chronic liver disease, and use of illicit injection drugs.
  • There may be an increased risk of fatal hepatitis in women, particularly black and Hispanic women. Risk also may be increased during the postpartum period.
  • Precise data on fatality rate for isoniazid-related hepatitis not available. There were 8 deaths among 174 cases of hepatitis in a US Public Health Service Surveillance Study that included 13,838 individuals.
  • Monitor and interview patients at monthly intervals. In addition, determine AST and ALT concentrations at baseline and periodically (monthly or more frequently as needed) in individuals ≥35 years of age and in individuals at increased risk of hepatitis.
  • Increases in serum transaminase concentrations occur in 10–20% of patients; these increases usually occur during the first few months of therapy but can occur at any time. Enzyme concentrations usually return to pretreatment values despite continued isoniazid therapy, but progressive liver dysfunction occurs in some cases.
  • Consider discontinuing isoniazid if liver function abnormalities are >3–5 times ULN.
  • Liver function tests are not a substitute for monthly clinical evaluations or for prompt assessment of signs or symptoms of adverse reactions that may occur between regularly scheduled evaluations.
  • Patients should be advised to immediately report prodromal symptoms of hepatitis to their clinician. (See Advice to Patients.)
  • Discontinue immediately if symptoms or signs suggestive of hepatic damage are detected; continued isoniazid use has been reported to cause a more severe form of liver damage.
  • Patients who have signs or symptoms of isoniazid-associated hepatic damage should be treated using alternative antituberculosis agents. If use of isoniazid is considered necessary, the drug should be restarted only after symptoms and laboratory abnormalities have cleared. In this situation, isoniazid should be restarted in very small dosages and gradually increased; discontinue immediately if there is any indication of recurrent liver involvement.
  • Use of isoniazid for treatment of latent tuberculosis infection (LTBI) should be deferred in patients with acute hepatic disease.

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