Sildenafil induces retinal vasodilatation in healthy subjects

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Abstract
Background: The cardiovascular effects of sildenafil (Viagra), a selective inhibitor of phosphodiesterase type 5 (PDE5), have been extensively studied. However, its effect on human retinal arteries and veins has not yet been investigated. The effect of a single dose administration of sildenafil on the retinal vessel diameters of healthy subjects was evaluated. Methods: Sildenafil 50 mg was administered to 10 healthy subjects (male:female = 4:6; mean age 31 (SD 6) years). The diameters of retinal arteries and veins were measured by means of a retinal vessel analyser (RVA) immediately before and at 30, 60, 90, and 120 minutes after sildenafil uptake. Blood pressure, heart rate, and intraocular pressure were monitored in parallel. Results: A significant increase of 5.8% (p<0.001) in both retinal arterial and venous diameters was found 30 minutes after sildenafil uptake. The diameters returned to baseline after 120 minutes. A mild systemic hypotensive response was seen. Changes in heart rate and intraocular pressure were not observed. Conclusion: Sildenafil causes a significant dilatation of retinal arteries and veins in healthy subjects. A possible role for PDE5 in the regulation of retinal blood flow is implicated.