isoniazid

Isoniazid is a small molecule antibiotic primarily used for the treatment and prevention of tuberculosis (TB). It acts as a prodrug that requires activation by the bacterial catalase-peroxidase enzyme KatG in Mycobacterium tuberculosis. Once activated, it forms an adduct with NAD+, which inhibits enoyl-acyl carrier protein reductase (InhA), thereby blocking mycolic acid synthesis—an essential component of the mycobacterial cell wall. This mechanism makes isoniazid bactericidal against actively dividing mycobacteria and bacteriostatic against dormant organisms. Isoniazid may also be used to treat infections caused by atypical mycobacteria such as M. avium, M. kansasii, and M. xenopi. It can be administered orally or intramuscularly and is often combined with other antimycobacterial agents to prevent resistance. The drug was first introduced in the early 1950s.

Brand names

NydrazidLaniazidHyzyd

Other names

isonicotinic acid hydrazide