OCULAR SAFETY OF VIAGRA (SILDENAFIL CITRATE): ACUTE STUDIES

The first study examined the effects of increasing doses of sildenafil on the results of several visual function tests. A double-blind, placebo-controlled, crossover, Phase II study assessed the acute effects (1 to 24 hours) of sildenafil (50 to 200 mg) in 16 healthy male volunteers. Sildenafil did not produce clinically significant changes in visual acuity, electroretinograms, intraocular pressure (IOP), contrast sensitivity, or pupillometry measurements compared with placebo. However, at single oral doses of 100 and 200 mg, transient impairment of color discrimination in the blue/green color range was detected using the Farnsworth-Munsell (FM) 100 hue test. These effects were fully reversible, and dose-related and occurred near the time of peak plasma concentration (1 to 2 hours after dosing).

A second study using only a single supratherapeutic dose (200 mg) of sildenafil (Viagra) in 8 healthy volunteers produced no clinically significant effects on visual field, visual acuity, photostress test, IOP, and ERGs. However, a modest increase in error score on the FM-100 hue test (blue-green) was again evident 1 to 2 hours postdose, resolving within 5 hours of dosing.

In a third study, 8 patients with early age-related macular degeneration were tested for the acute effects of 100 mg of sildenafil. The study was placebo-controlled, randomized and double-blind with cross-over design. The patients underwent a battery of tests that included visual acuity, Humphrey perimetry, color discrimination D15 test, photostress, and Amsler grid. A detailed description of study results is just now in preparation (Data on file, Pfizer Central Research). However, in brief summary, they disclosed no special susceptibility as the study medication had little to no effect on visual performance in any of the subjects.

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