title: Effect of sildenafil citrate (Viagra) on the ocular circulation.
abstract: OBJECTIVE
  Sildenafil citrate induces vasodilation by enhancing the smooth muscle relaxant effects of nitric oxide. We have previously reported that nitrate compounds, a different group of nitric oxide-mediated vasodilators used mainly for the treatment of ischemic cardiac diseases, produce an increase in optic nerve head circulation and retinal venous vasodilation. The purpose 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 volunteers received 100-mg doses of sildenafil citrate (Viagra; Pfizer, Inc, New York, New York) or matching placebo on 2 separate days. Laser Doppler flowmetry was used to assess foveolar choroidal and optic nerve rim circulatory parameters. Measurements were obtained in one eye at baseline, 1 hour, and 5 hours after dosing. Blood pressure and intraocular pressure were monitored, 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 change in mean blood pressure, intraocular pressure, perfusion pressure, or choroidal or optic nerve circulatory parameters were observed after sildenafil treatment. The power to detect a 20% change in optic nerve head and choroidal blood flow after sildenafil was approximately 90%.
  
  
  CONCLUSIONS
  In comparison with placebo, no significant change in optic nerve rim or foveolar choroidal blood flow was observed after treatment with sildenafil. This suggests that nitrate compounds and sildenafil may differentially affect ocular circulation. Furthermore, no significant effects on intraocular pressure, systemic blood pressure, or ocular perfusion pressure were detected after sildenafil treatment.
authors.affiliation: Scheie Eye Institute, Department of Ophthalmology, University of Pennsylvania, Philadelphia, Pennsylvania, USA. juangrun@mail.med.upenn.edu
authors.forename: J E
authors.initials: JE
authors.lastname: Grunwald
authors.forename: K K
authors.initials: KK
authors.lastname: Siu
authors.forename: S S
authors.initials: SS
authors.lastname: Jacob
authors.forename: J
authors.initials: J
authors.lastname: Dupont
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D002829:Choroid / Q000098:blood supply; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005123:Eye / Q000098:blood supply*; D006801:Humans; D007429:Intraocular Pressure / Q000187:drug effects; D008297:Male; D009898:Optic Disk / Q000098:blood supply; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology*; D011687:Purines; D012039:Regional Blood Flow / Q000187:drug effects; D000068677:Sildenafil Citrate; D013450:Sulfones; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D014665:Vasodilator Agents; D000068677:Sildenafil Citrate