Ketotifen

Ketotifen is a benzocycloheptathiophene derivative with dual pharmacological activity: it competitively blocks H1 histamine receptors providing antiallergic effects, and it stabilizes mast cell membranes inhibiting degranulation and release of histamine, leukotrienes, and other inflammatory mediators. This dual antihistamine-plus-mast-cell-stabilizer mechanism distinguishes it from pure H1 antagonists, providing prophylactic benefit in allergic asthma and conjunctivitis when used regularly.

Adult

For allergic rhinitis: 1 mg twice daily, increased if necessary to 2 mg twice daily, to be taken with food. For allergic rhinitis in readily sedated patients: Initially 0.5–1 mg once daily, dose to be taken at night. For allergic conjunctivitis (ophthalmic): Apply twice daily; increased if necessary to 4 times a day, maximum duration of treatment 6 weeks.

Pediatric

For allergic rhinitis (Child 3–17 years): 1 mg twice daily. For allergic conjunctivitis (Child 12–17 years, ophthalmic): Apply twice daily; increased if necessary to 4 times a day, maximum duration of treatment 6 weeks.

Renal adjustment

Reduce daily dose by half in moderate to severe renal impairment.

Hepatic adjustment

Manufacturer advises caution in mild to moderate impairment (increased risk of accumulation); avoid in severe impairment. Dose reduction of 33% in mild to moderate impairment.

Max dose

4 mg per day (oral, for allergic rhinitis)

• Acute porphyrias
• Epilepsy
• Prostatic hypertrophy (in adults)
• Pyloroduodenal obstruction
• Susceptibility to angle-closure glaucoma
• Urinary retention