Isoniazid
TREATMENT
Isoniazid (INH; 300 mg PO q24h) exerts bactericidal effects by interfering with the synthesis of lipid components of the mycobacterial cell wall. INH is a component of most TB treatment regimens and can be given twice a week in directly observed therapy (15 mg/kg/dose; 900 mg maximum).
INH remains the drug of choice for treatment of latent TB infection (300 mg PO q24h for 9 mo or combined with rifapentine in a 12-wk regimen).SPECIAL CONSIDERATIONS
Adverse events primarily consist of elevations in LFTs (~20%). This effect can be idiosyncratic but is usually seen with advanced age, underlying liver disease, or concomitant consumption of alcohol and may be potentiated by rifampin. Transaminase elevations to greater than threefold the upper limit of the normal range necessitate holding therapy. Patients with known liver dysfunction should have weekly LFTs monitored during the initial stage of therapy. INH also antagonizes vitamin B6 metabolism and can potentially cause peripheral neuropathy. INH should always be coadministered with pyridoxine 25-50 mg PO daily to minimize the risk of neuropathies, especially in the elderly and pregnant women, as well as in patients with diabetes, renal failure, alcoholism, and seizure disorders.