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.

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.