Effects of sildenafil on retinal blood flow and flicker-induced retinal vasodilatation in healthy subjects.
OBJECTIVE
Sildenafil is a specific inhibitor of phosphodiesterase V, which is widely used for the treatment of erectile dysfunction. Sildenafil has been shown to induce vasodilation in several vascular beds by inhibiting the cGMP breakdown. The present study was conducted to investigate whether sildenafil increases blood flow in the human retina.


METHODS
In a randomized, double-masked, placebo-controlled, two-way crossover study in 12 healthy male volunteers the effects of a single dose of 100 mg sildenafil were studied. Subjects received sildenafil or placebo on two different study days. After administration, retinal hemodynamic parameters were measured every 20 minutes. Retinal vessel diameters and retinal blood velocity were assessed with the retinal vessel analyzer and bidirectional laser Doppler flowmetry, respectively. In addition, the response of retinal vessel diameters to stimulation with diffuse flicker light was studied. Blood pressure and intraocular pressure were measured with noninvasive techniques.


RESULTS
Sildenafil had no effect on mean arterial pressure, pulse rate, intraocular pressure, retinal blood velocity, or retinal arterial diameter. However, a significant increase in retinal venous diameters (4.7% +/- 3.2%; P=0.0028 versus placebo) and retinal blood flow 15.7% +/- 18.0%; P=0.029 versus placebo) was observed. Sildenafil had no effect on flicker-induced vasodilation in retinal arteries or veins.


CONCLUSIONS
The data indicate that sildenafil increases retinal venous diameters and retinal blood flow in healthy subjects. By contrast, it does not affect intraocular pressure and flicker-induced retinal vasodilation. Further studies are needed to elucidate whether this drug may be therapeutically used in retinal ischemic disease.
Department of Clinical Pharmacology, University of Vienna, Austria.
Kaija
K
Polak
Barbara
B
Wimpissinger
Fatmire
F
Berisha
Michael
M
Georgopoulos
Leopold
L
Schmetterer
D015106:3',5'-Cyclic-GMP Phosphodiesterases / Q000037:antagonists & inhibitors; D000328:Adult; D001783:Blood Flow Velocity / Q000187:drug effects; D001794:Blood Pressure; D018592:Cross-Over Studies; D004311:Double-Blind Method; D006339:Heart Rate; D006801:Humans; D007429:Intraocular Pressure; D017078:Laser-Doppler Flowmetry; D008297:Male; D008875:Middle Aged; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology*; D010879:Piperazines / Q000494:pharmacology*; D011687:Purines; D012039:Regional Blood Flow / Q000187:drug effects; D012171:Retinal Vessels / Q000502:physiology*; D000068677:Sildenafil Citrate; D013450:Sulfones; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology*
D010726:Phosphodiesterase Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D014665:Vasodilator Agents; D000068677:Sildenafil Citrate; D015106:3',5'-Cyclic-GMP Phosphodiesterases