Viagra (sildenafil) is a brand-name prescription drug that’s used to treat erectile dysfunction (ED). Learn about side effects, warnings, dosage, and more. Detailed Sildenafil dosage information for adults, the elderly and children. Includes dosages for Erectile Dysfunction and Pulmonary Hypertension; plus renal, liver and dialysis adjustments. 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. Sildenafil oral tablet is a prescription medication used to treat erectile dysfunction (ED) and pulmonary arterial hypertension (PAH). Sildenafil is used to treat erectile dysfunction in adult men or pulmonary arterial hypertension in adults and children, depending on the brand or formulation. Includes sildenafil side effects, interactions, and indications. Sildenafil is a treatment for erectile dysfunction. It works by increasing blood flow to your penis. Sildenafil, sold under the brand name Viagra among others, is a medication used to treat erectile dysfunction and pulmonary arterial hypertension. [4][8] It is also sometimes used off-label for the treatment of certain symptoms in secondary Raynaud's phenomenon. [9] Sildenafil works by blocking an enzyme in the body called PDE5, which helps relax certain blood vessels. For erectile dysfunction, it increases blood flow to the penis when aroused. Sildenafil is used to treat erectile dysfunction (also called sexual impotence). Sildenafil belongs to a group of medicines called phosphodiesterase 5 (PDE5) inhibitors. Information about the drug sildenafil (Viagra) prescribed for the treatment of impotence (erectile dysfunction, ED) and pulmonary arterial hypertension. Side effects, drug interactions, and dosing information is included.