Both Viagra and the metabolite feature pole half lives of virtually 4 hours. The refuge andefficacy of Sildenafil with other PDE5 inhibitors, including REVATIO, get not beenstudied [see WARNINGS AND PRECAUTIONS]. Physicians should warn patientsthat drawn-out erections greater than 4 hours and priapism (afflictive erectionsgreater than 6 hours in duration)…...