Viagra and alcohol: what are the rules? Answer: In short, the drug in Viagra, Sildenafil, dilates blood vessels at the entrance to the penis. More harmful side effects tend to be uncommon or rare. In healthy male volunteers, there was no evidence of a clinically significant effect of azithromycin mg daily for 3 days on the systemic exposure of sildenafil or its major circulating metabolite. This is especially true if your problems involve someone else, such as your partner. These patients had erectile dysfunction at baseline that was characterized by median categorical scores of 2 a few times on principal IIEF questions. · Viagra; Descriptions. Sildenafil is used to treat men who have erectile dysfunction (also called sexual impotence). Sildenafil belongs to a group of medicines called phosphodiesterase 5 (PDE5) inhibitors. These medicines prevent an enzyme called phosphodiesterase type-5 from working too quickly. The penis is one of the areas where . Typical dosing for Sildenafil (Viagra) The typical dose is to take 50 mg of sildenafil (Viagra) by mouth, about 1 hour before sex, as needed. The maximum recommended dose is mg. Don’t take sildenafil (Viagra) more than once daily (at any dose). Written by Brian Leonard, PharmD, BCACP, test1.rug: miami.  · How we vet brands and products. If you’re interested in buying Viagra online, five of the best options available are Hims, Roman, Lemonaid, Optum Store, and REX MD. Read on for full details on.