PURPOSE: To determine the duration of action of ketotifen 0.025% eye drops vs placebo taken as single or multiple doses in an allergen challenge model. DESIGN: Two randomized, multicenter, double-masked, contralateral placebo-controlled studies, one a single-dose and one a multiple-dose study. METHODS: Two conjunctival provocation tests (CPTs) were initially conducted to confirm reproducibility of subject responses in both studies. Subjects in study 1 (n = 87) received single doses of ketotifen in one eye and placebo in the other 15 minutes, 6 hours, and 8 hours before CPT. Subjects in study 2 (n = 85) received ketotifen or placebo once 8 hours before CPT. Single-dose efficacy results were used to further qualify a subject as a responder. Responders were re-randomized to a 4-week twice daily dosing regimen with a CPT 8 hours after the final dose. In both studies, ocular symptoms were assessed at three time points 3 to 15 minutes after challenge. There were no significant differences in adverse events between groups. RESULTS: For both studies, ocular itching and vascular injection were significantly reduced (P < .003) at all time points after instillation of ketotifen, with a maximum reduction at 7 minutes postchallenge. In study 2, chemosis, tearing, and lid swelling were also assessed and were significantly reduced (P < .008) after instillation of ketotifen. CONCLUSIONS: Ketotifen 0.025% eye drops were safe and statistically effective in preventing ocular itching, injection, and other signs and symptoms of allergic conjunctivitis at 15 minutes, 6 hours, and 8 hours after a single dose and at 8 hours after the final dose of a 4-week twice daily regimen.
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