The effect of sildenafil citrate (Viagra) on visual sensitivity.

The erectile dysfunction medicine sildenafil citrate (Viagra) inhibits phosphodiesterase type 6 (PDE6), an essential enzyme involved in the activation and modulation of the phototransduction cascade. Although Viagra might thus be expected to impair visual performance, reports of deficits following its ingestion have so far been largely inconclusive or anecdotal. Here, we adopt tests sensitive to the slowing of the visual response likely to result from the inhibition of PDE6.

Factors that predict changing the type of phosphodiesterase type 5 inhibitor medication among men in the UK.

Objective: To evaluate predictors of changing the type of phosphodiesterase type 5 (PDE5) inhibitor (switching) among men with erectile dysfunction (ED) in the UK, the largest consumer of PDE5 inhibitors in Europe, as switching medication is often associated with higher resource use, and there are three oral PDE5 inhibitor medications currently available.

Patients And Methods: Patients were identified from The Health Improvement Network database in the UK; men initiating therapy with sildenafil, tadalafil or vardenafil from May 2003 to August 2004 with >/= 6 months of prescription history before and after their initial PDE5 inhibitor prescription were included. Switching was evaluated as the proportion of second PDE5 inhibitor prescriptions that were for a drug differing from the first.