Name: Isoniazid (INH)
Class: Antitubercular
Mech.: Tuberculostatic to resting bacilli, tuberculocidal to rapidly dividing cells. Enters cells via active uptake. Interferes w/DNA synth, glycolyis, synth of mycolic acid (unique component of mycobacteria)
Absorption: Rapidly absorbed after oral admin.
Distribution: Distributes in total body water. Retained in infected tissue.
Metab.: Acetylated in liver.
Excretion, t½: Urine. 75-90% in urine as metabolites in 24 hrs.
Toxicity/S.E.s: Direct—inactivation/depletion of pyridoxine ® peripheral neuritis (treat prophylactically w/supplemental pyridoxine). Hypersensitivity rxns. Hepatitis (can be fatal) due to toxic metabolites. Convulsions, optic neuritis, toxic encephalopathy, reversible psychotic episodes.
Utility: Most important and widely used drug for tuberculosis. Prob. w/resistance.
Special Features: Only drug approved for prophylaxis of tuberculosis.