Isoniazid is a bactericidal agent active against organisms of the genus Mycobacterium, specifically M. tuberculosis, M. bovis and M. kansasii. Isoniazid is recommended for all forms of tuberculosis in which organisms are susceptible. Isoniazid is a prodrug and must be activated by bacterial catalase. Isoniazid inhibits InhA, the enoyl reductase from Mycobacterium tuberculosis, by forming a covalent adduct with the NAD cofactor. The most frequent adverse reactions to isoniazid are those affecting the nervous system and the liver.

Isonicotinamide is the amide form of isonicotinic acid. It is often used as a scaffold for other synthetic compounds. Isonicotinamide has been identified as inducing apoptosis through DNA fragmentation in leukemia cell models and has been studied in mice or the prevention of diabetes. Isonicotinamide activates the NAD-dependent histone deacetylase SIR2 by raising intracellular NAD+ concentration.

Isonicotinic acid considered to be inactive isomer of nicotinic acid. Isonicotinic acid is a metabolite of pyridine-4-carboxy hydrazide (isonicotinyl hydrazide; isoniazid) a front-line weapon in the battle against tuberculosis. Isonicotinic acid and its derivatives are used in manufacturing pharmaceuticals and agrochemicals.

Methaniazide (metaniazide) is the methanesulfonate derivative of isoniazid with antibacterial properties. It is used used primarily as a tuberculostatic. It remains the treatment of choice for tuberculosis.

Pasiniazid is a composition of isoniazid and 4-aminosalicylic acid, that has mutual effects coupling isoniazid and 4-aminosalicylic acid for use in tuberculosis patients. Isoniazid is a bactericidal agent active against organisms of the genus Mycobacterium, specifically M. tuberculosis, M. bovis and M. kansasii. Isoniazid is a prodrug and must be activated by bacterial catalase. Isoniazid inhibits InhA, the enoyl reductase from Mycobacterium tuberculosis, by forming a covalent adduct with the NAD cofactor. 4-Aminosalicylic acid is an anti-tuberculosis drug used to treat tuberculosis in combination with other active agents. There are two mechanisms responsible for aminosalicylic acid's bacteriostatic action against Mycobacterium tuberculosis. Firstly, aminosalicylic acid inhibits folic acid synthesis (without potentiation with antifolic compounds). The binding of para-aminobenzoic acid to pteridine synthetase acts as the first step in the folic acid synthesis. Aminosalicylic acid binds pteridine synthetase with greater affinity than para-aminobenzoic acid, effectively inhibiting the synthesis of folic acid. As bacteria are unable to use external sources of folic acid, cell growth and multiplication slow. Secondly, the aminosalicylic acid may inhibit the synthesis of the cell wall component, mycobactin, thus reducing iron uptake by M. tuberculosis.

Methaniazide (metaniazide) is the methanesulfonate derivative of isoniazid with antibacterial properties. It is used used primarily as a tuberculostatic. It remains the treatment of choice for tuberculosis.