Sildenafil: efficacy, safety, tolerability and mechanism of action in treating erectile dysfunction.

Sildenafil citrate is marketed under the trademark name Viagra and is widely used to treat male erectile dysfunction; therapeutic uses of this medication for other diseases related to vascular dysfunction are emerging. When used as recommended, the drug has a strong clinical efficacy and safety profile in a broad spectrum of the male population. Its widespread use and effects of long-term exposure to the drug due to particular treatment regimens or inappropriate use mandate an ongoing update of its molecular mechanism, pharmacological profile and associated safety issues. This review focuses on biochemical and pharmacological features of sildenafil, the active component in Viagra, interaction of sildenafil with phosphodiesterase 5, pharmacokinetic parameters, action in smooth muscle, side effects, safety profile and prospects for other uses.