Ketotifen is an organic heterotricyclic compound, specifically 4,9-dihydro-10H-benzo[4,5]cyclohepta[1,2-b]thiophen-10-one, substituted at position 4 with a 1-methylpiperidin-4-ylidene group. It is an H1-receptor antagonist and anti-asthmatic drug, typically used as its hydrogen fumarate salt. It stabilizes mast cells and acts as a histamine H1 receptor blocker, with full therapeutic effect often taking several weeks to manifest. It is classified as an organosulfur heterocyclic compound, cyclic ketone, piperidine, olefinic compound, tertiary amino compound, and conjugate base of ketotifen(1+).
