Therapeutic Classification: antituberculars
Absorption: Well absorbed following PO/IM administration.
Distribution: Widely distributed; readily crosses the blood-brain barrier.
Metabolism/Excretion: 50% metabolized by the liver by N-acetyltransferase (rate of acetylation is genetically determined [slow acetylators have ↑ isoniazid levels and ↑ risk of toxicity; fast acetylators have ↓ isoniazid levels and ↑ risk for treatment failure]); 50% excreted unchanged by the kidneys.
Half-Life: 1–4 hr in patients with normal renal and hepatic function; 0.5–1.6 hr in fast acetylators; 2–5 hr in slow acetylators.
