Ketotifen

How it works

It blocks histamine H1 receptors and stabilises mast cells to reduce the release of inflammatory mediators, relieving the itching, redness and watering of allergic conjunctivitis.

Prescribing in practice

• Preservatives such as benzalkonium chloride in some formulations can be absorbed by soft contact lenses and cause ocular irritation, so lenses should be removed before instillation and reinserted only after a suitable interval.
• Transient stinging or burning and, rarely, mild drowsiness may occur.
• Used for symptomatic relief of allergic conjunctivitis and is generally well tolerated for seasonal use.

Monitoring

No systemic monitoring is required; review symptom control clinically and reassess if symptoms persist or worsen.

Counselling the patient

• Remove soft contact lenses before instilling and wait the recommended interval before reinserting them.
• Brief blurring or stinging may occur after instillation, so wait until vision clears before driving.

Evidence & guidelines

Topical antihistamine and mast cell stabilising drops are recommended for allergic conjunctivitis in NICE Clinical Knowledge Summaries.