Phosphodiesterase 5 inhibition: effects on the coronary vasculature.

As a potent and selective inhibitor of cyclic guanosine monophosphate-specific phosphodiesterase 5 (PDE5), sildenafil citrate (Viagra) is safe and effective in men with erectile dysfunction (ED) of diverse aetiologies, including patients with common cardiovascular diseases who are not receiving organic nitrates or nitrate donor drugs. In retrospective analyses of extensive clinical trials, sildenafil treatment for ED was not associated with any increase in cardiac risk. In haemodynamic studies, sildenafil produced small decreases in systemic and pulmonary blood pressure but caused no adverse cardiovascular effects in specific populations of men with coronary heart disease. Sildenafil also caused no significant changes in coronary blood flow but had a positive effect on coronary flow reserve in men with severe coronary artery disease. Together with findings from other studies, these data suggest that PDE5 may play an important role in the regulation of coronary blood flow in the healthy and diseased heart.