About Isoniazid Hydrazine derivative, Antitubercular Agent. Mechanism of Action of Isoniazid Isoniazid is a bactericidal drug. I t inhibits the mycolic acid synthesis which is essential for the cell wall formation. It also inhibits DNA, RNA and protein synthesis and cell metabolism. As the results of these bacterial death occurs. Indications for Isoniazid 1.Tuberculosis (pulmonary &extra pulmonary) Interactions for Isoniazid Alcohol: Regular ingestion of alcohol is associated with higher incidence of INH-related hepatitis. Aluminium Salts: Oral absorption of INH reduced leading to decreased serum levels. Oral anticoagulants: Efficacy of oral anticoagulants increased. Benzodiazepines: Activity of benzodiazepines that undergo oxidative metabolism is possibly increased. Carbamazepine: Isoniazid hepatotoxicity & carbamazepine toxicity may occur from concurrent use. Cycloserine: Increased cycloserine related CNS side effects, especially dizziness.