Objective: To investigate the effect of a single-dose and 2-week administration of topical 0.25% verapamil on episcleral venous pressure (EVP) and intraocular pressure (IOP). Design: A prospective, randomized, double- masked, crossover, and placebo-controlled study. Participants: One eye of each of 20 normal subjects received topical verapamil or placebo. Intervention: The EVP was measured using a pressure chamber episcleral renomanometer. The IOP, EVP, heart rate (HR), and blood pressure (BP) were measured at baseline, 1.5 hours after a single drop, and after 2-week, three- times-a-day topical administration of 0.25% verapamil or placebo to one eye. After a 4-week washout period, the treatment to the study eye was reversed, and measurements of EVP, IOP, HR, and BP were repeated. Main Outcome Measures: The EVP, IOP, HR, and BP were measured. Results: Ninety minutes after a single drop, the EVP in the verapamil-treated eyes was reduced by 4.8% (P = <0.001) and in the untreated fellow eyes by 2.4% (P = 0.032). After 2-week topical administration, the EVP was reduced by 9.5% (P = <0.0001) in the verapamil-treated eyes and by 4.8% (P = 0.001) in the fellow eyes. The EVP was unchanged in the treated and fellow eyes after a single drop or after a 2-week treatment with placebo. Ninety minutes after topical administration of 0.25% verapamil, the IOP decreased by 7.7% (P = <0.0001) in the treated eyes and decreased by 3.6% (P = 0.03) in the fellow eyes. After a 2-week administration of topical verapamil, the IOP decreased by 12% (P = 0.0001) in the treated eyes and by 7.2% (P = 0.0289) in the fellow eyes. The changes of IOP in the placebo-treated and fellow eyes were not statistically significant after a single-dose and 2-week administration. After topical administration of verapamil, a contralateral effect on IOP and EVP was observed in the fellow, untreated eye. No systemic effect on HR or BP was detected after a single-dose administration of topical verapamil. There were, however, significant reductions in HR and BP after a 2-week treatment with topical 0.25% verapamil. Conclusion: These results indicate that a single drop and a 2-week administration of topical 0.25% verapamil decrease IOP and EVP significantly, with more pronounced reduction after a 2-week treatment than after a single-dose treatment.
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