Isoniazid

Molecular formula: C6H7N3O
Molecular weight: 137.14
CAS No.: 54-85-3 
Isoniazid is an antibacterial drug (trade name Nydrazid) used to treat tuberculosis. Also known as isonicotinic acid hydrazide, isoniazid is the most effective antituberculosis drug currently available. The drug inhibits or kills the tubercle bacilli that cause the disease. It is usually given together with some other antituberculosis drug such as streptomycin or aminosalicylic acid to prevent emergence of drug resistant organisms (see drug resistance ). To prevent development of resistant tuberculosis bacteria, people with tuberculosis are treated with long courses of combination drug therapy, most commonly isoniazid, rifampin, and pyrazinamide. 
Isoniazid is the most effective tuberculostatic agent.