title: Effect of sildenafil citrate (Viagra) on retinal blood vessel diameter.
abstract: OBJECTIVE
  The present investigation was conducted to evaluate the effect of sildenafil citrate (Viagra, Pfizer Inc., New York, NY) on retinal blood vessel diameter.
  
  
  METHODS
  Double-blind randomized, placebo-controlled, cross-over study.
  
  
  METHODS
  Fifteen healthy male volunteers (mean age 39 years) received 100-mg doses of sildenafil or matching placebo on 2 separate days. Monochromatic fundus photography was obtained in one eye, and brachial artery blood pressure and intraocular pressure were measured at baseline, 1 hour, and 5 hours after dosing. The diameters of two major temporal veins and one artery were measured in a masked fashion from digitized photographic negatives.
  
  
  RESULTS
  In comparison with placebo, no statistically significant change in average venous diameter was observed for the superior (analysis of variance [ANOVA], P =.97), inferior retinal temporal vein (ANOVA, P =.73), or the retinal temporal artery (ANOVA, P =.89) after sildenafil treatment. In comparison to placebo, there was no significant difference in the percentage change from baseline in venous or arterial diameter at 1 or 5 hours after sildenafil. The power to detect a 6.5% change in retinal vascular diameter following sildenafil was approximately 80% (P =.05).
  
  
  CONCLUSIONS
  These data suggest that at the maximum therapeutic dose used clinically (100 mg), sildenafil does not have a significant effect on retinal vascular caliber.
authors.affiliation: Scheie Eye Institute, Department of Ophthalmology, University of Pennsylvania, Philadelphia, 19104, USA. juangrun@mail.med.upenn.edu
authors.forename: Juan E
authors.initials: JE
authors.lastname: Grunwald
authors.forename: Tatyana
authors.initials: T
authors.lastname: Metelitsina
authors.forename: Lili
authors.initials: L
authors.lastname: Grunwald
mesh_terms: D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000037:antagonists & inhibitors*; D000328:Adult; D001783:Blood Flow Velocity / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D018592:Cross-Over Studies; D004311:Double-Blind Method; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007429:Intraocular Pressure / Q000187:drug effects; D008297:Male; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D010781:Photography; D010879:Piperazines / Q000494:pharmacology*; D011687:Purines; D012039:Regional Blood Flow; D012171:Retinal Vessels / Q000187:drug effects*; D000068677:Sildenafil Citrate; D013450:Sulfones; D014664:Vasodilation; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D014665:Vasodilator Agents; D000068677:Sildenafil Citrate; D015106:3',5'-Cyclic-GMP Phosphodiesterases