Effect of sildenafil citrate (Viagra) on the ocular circulation

PURPOSE: Sildenafil citrate induces vasodilation by enhancing the smooth mu scle relaxant effects of nitric oxide, We have previously reported that nit rate com pounds, a different group of nitric oxide-mediated vasodilators us ed mainly for the treatment of ischemic cardiac diseases, produce an increa se in optic nerve head circulation and retinal venous vasodilation. The pur pose of the present investigation was to evaluate the effect of sildenafil on ocular circulation. METHODS: In a double-blind, randomized, crossover trial, 15 healthy male vo lunteers received 100-mg doses of sildenafil citrate (Viagra; Pfizer, Inc, New York, New York) or matching placebo on 2 separate days. Laser Doppler f lowmetry was used to assess foveolar choroidal and optic nerve rim circulat ory parameters. Measurements were obtained in one eye at baseline, 1 hour, and 5 hours after dosing. Blood pressure and intraocular pressure were moni tored, and perfusion pressure was calculated. RESULTS: Mean optic nerve head blood flow measurements at baseline, 1 hour, and 5 hours were 11.6 +/- 2,2 arbitrary units (+/- SD), 12.5 +/- 2.8, and 12,1 +/- 2.4 after sildenafil and 11.9 +/- 2.5, 12.6 +/- 3.1, and 13.0 + 3. 0 after placebo, respectively. When compared with placebo, no significant c hange in mean blood pressure, intraocular pressure, perfusion pressure, or choroidal or optic nerve circulatory parameters were observed after sildena fil treatment. The power to detect a 20% change in optic nerve head and cho roidal blood flow after sildenafil was approximately 90%. CONCLUSIONS: In comparison with placebo, no significant change in optic ner ve rim or foveolar choroidal blood flow was observed after treatment with s ildenafil. This suggests that nitrate compounds and sildenafil may differen tially affect ocular circulation. Furthermore, no significant effects on in traocular pressure, systemic blood pressure, or ocular perfusion pressure w ere detected after sildenafil treatment. (Am J Ophthalmol 2001; 131:751-755 . (C) 2001 by Elsevier Science Inc. All rights reserved.).