Sildenafil (Viagra)

Sildenafil is commonly used for the following conditions.

Erectile dysfunction, a condition where you have trouble getting or keeping an erection
Pulmonary arterial hypertension, a condition where you have high blood pressure in the blood vessels that carry blood from your heart to your lungs
Sildenafil may also be used for other conditions as determined by your healthcare provider.

How does sildenafil work (mechanism of action)?
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. This makes it easier to get and keep an erection. For pulmonary arterial hypertension, sildenafil relaxes the blood vessels in the lungs. This lowers blood pressure and reduces strain on the heart.