Ketotifen

Generic Name: Ketotifen

Brand Names: Alaway, Zaditen, Zaditor

Drug Type: Small Molecule

Chemical Formula: C_₁₉H_₁₉NOS

CAS Number: 34580-13-7

Unique Ingredient Identifier: X49220T18G

Overview

Ketotifen is a benzocycloheptathiophene derivative with potent antihistaminic and mast cell stabilizing properties. It has a similar structure to some other first-generation antihistamines such as cyproheptadine and azatadine. Ketotifen was first developed in Switzerland in 1970 by Sandoz Pharmaceuticals and was initially marketed for the treatment of anaphylaxis. In the US, it is now used in an over-the-counter ophthalmic formulation for the treatment of itchy eyes associated with allergies, and in Canada a prescription-only oral formulation is available and indicated as an add-on therapy for children with atopic asthma. In addition, oral ketotifen is used in Mexico and across Europe for the treatment of various allergic symptoms and disorders, including urticaria, mastocytosis, and food allergy.

Background

Indication

Administered orally, ketotifen is indicated as an add-on medication in the chronic treatment of mild atopic asthma in children. It is also available as an over-the-counter ophthalmic solution which is indicated for the temporary prevention of itching of the eye due to allergic conjunctivitis.

Associated Conditions

Allergic Rhinitis (AR)
Asthma, Allergic
Eye pruritus
Seasonal Allergic Conjunctivitis

Research Report

Published: Apr 30, 2025

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 C19H19NOS [1], with a corresponding molecular weight of approximately 309.43 g/mol.[1] The fumarate salt has the molecular formula C23H23NO5S and a molecular weight of 425.50 g/mol.[5] The distinction between the base and the salt form is critical,

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