Comprehensive Report: Ketotifen

I. Introduction and Drug Identification

• A. Overview of Ketotifen Ketotifen is a pharmaceutical agent recognized for its utility in managing various allergic conditions. Its therapeutic action stems from a dual mechanism, functioning both as a histamine H1 receptor antagonist (antihistamine) and as a mast cell stabilizer.3 This combination of activities allows it to address different facets of the allergic response. The drug is available in multiple formulations tailored for specific applications. Ophthalmic preparations, including eye drops and, more recently, drug-eluting contact lenses, are primarily employed for the symptomatic relief of allergic conjunctivitis, targeting ocular itching and irritation.3 Oral formulations, such as tablets and syrups, are utilized systemically for the prophylaxis of mild atopic asthma, particularly in pediatric populations in certain regions, and for the management of other allergic-type disorders.3
• B. Chemical Properties Ketotifen belongs to the benzocycloheptathiophene class of compounds.4 Chemically, the base form is identified as 4-(1-Methyl-4-piperidinylidene)-4,9-dihydro-10H-benzo1cyclohepta[1,2-b]thiophen-10-one.2 However, it is frequently formulated and administered as its hydrogen fumarate salt.5 The IUPAC name for the base is 2-(1-methylpiperidin-4-ylidene)-6-thiatricyclo[8.4.0.03,7]tetradeca-1(14),3(7),4,10,12-pentaen-8-one 4, while the fumarate salt is named (E)-but-2-enedioic acid;2-(1-methylpiperidin-4-ylidene)-6-thiatricyclo[8.4.0.03,7]tetradeca-1(14),3(7),4,10,12-pentaen-8-one.7 Variations in nomenclature exist across sources.4 The molecular formula for the ketotifen base is C19​H19​NOS [1], with a corresponding molecular weight of approximately 309.43 g/mol.[1] The fumarate salt has the molecular formula C23​H23​NO5​S and a molecular weight of 425.50 g/mol.[5] The distinction between the base and the salt form is critical,