Overview
Ketotifen is a second-generation antihistamine and mast cell stabilizer used primarily for the prevention and treatment of allergic conditions. It has both H1-antihistamine properties and inhibits the release of inflammatory mediators from mast cells. Ketotifen is available in oral and ophthalmic formulations, with the oral form commonly used for allergic conditions like asthma, allergic rhinitis, and atopic dermatitis, while the ophthalmic solution is used for allergic conjunctivitis.
Mechanism of Action
Ketotifen exerts its effects through multiple mechanisms: 1) Competitive antagonism of histamine at H1-receptors, blocking histamine-mediated allergic responses. 2) Inhibition of mast cell degranulation, preventing release of histamine, leukotrienes, and other inflammatory mediators. 3) Possible anti-inflammatory effects through inhibition of eosinophil chemotaxis and platelet-activating factor (PAF).
Indications
- Prophylaxis of bronchial asthma (particularly in children)
- Allergic rhinitis
- Allergic conjunctivitis (ophthalmic formulation)
- Atopic dermatitis
- Urticaria and other allergic skin conditions
Dosage
Adults and children over 3 years: 1 mg twice daily (morning and evening). Children 6 months to 3 years: 0.5 mg twice daily. May be taken with food to minimize gastrointestinal side effects. For ophthalmic use: One drop in affected eye(s) twice daily, approximately 8-12 hours apart.
Contraindications
- Hypersensitivity to ketotifen or any component of the formulation
- Acute asthma attacks (not for relief of acute bronchospasm)
- Concurrent use with monoamine oxidase inhibitors (MAOIs)
Side Effects
- Drowsiness/sedation (most common)
- Dry mouth
- Weight gain
- Increased appetite
- Dizziness
- Headache
- Nausea
- Fatigue
- Nervousness
- Ophthalmic: Eye irritation, conjunctival injection, keratitis, photophobia
Interactions
- CNS depressants (alcohol, benzodiazepines, opioids): Enhanced sedative effects
- Monoamine oxidase inhibitors (MAOIs): Contraindicated due to risk of severe adverse reactions
- Anticholinergic drugs: May enhance anticholinergic effects
- Theophylline: Ketotifen may increase theophylline levels