Pfizer to lose patent of drug Viagra, Indian companies gear up with copycat versions: Pfizer's patent for the formulation of Viagra, used to treat impotence in men, ends in the US in 2020. Sildenafil (Viagra) is a tablet that's taken by mouth for erectile dysfunction (ED) in adults. It works as a phosphodiesterase-5 (PDE5) inhibitor to help people get an erection or keep an erection that lasts for sex. Viagra (sildenafil) is a brand-name prescription drug that’s used to treat erectile dysfunction (ED). Learn about side effects, warnings, dosage, and more. Learn more about Viagra, including its uses, dosage, side effects, and how to get it. Viagra relaxes muscles found in the walls of blood vessels and increases blood flow to particular areas of the body. Viagra is used to treat erectile dysfunction (impotence) in men. Evidence-based academic analysis of sildenafil citrate: mechanism, pharmacokinetics, clinical efficacy, and safety profile. Find patient medical information for Sildenafil (Viagra, Revatio) on WebMD including its uses, side effects and safety, interactions, pictures, warnings, and user ratings “The little blue pill” known as Viagra is the world’s most popular erectile dysfunction medicine. It’s also the source of many inaccurate medical myths. Viagra is used to treat problems relating to male sexual function, particularly problems concerning the ability to achieve and maintain an erection. Learn how to take Viagra safely to treat erectile dysfunction. Swallow a 50 mg dose of Viagra 30-60 minutes before sex. Erectile dysfunction is a condition where the penis does not harden and expand when a man is sexually excited, or when he cannot keep an erection. When a man is sexually stimulated, his body's normal response is to increase blood flow to his penis to produce an erection.