The sildenafil compound was originally developed by Pfizer for the treatment of hypertension (high blood pressure) and angina pectoris (chest pain due to heart disease). During the heart clinical trials, researchers discovered that the drug was more effective at inducing erections than treating angina.

Pfizer realized ED was an unmet medical need and a major opportunity for financial gain. In 1998, the FDA approved Viagra, the first oral treatment for erectile dysfunction, under a priority review.

Sildenafil, sold under the brand name Viagra among others, is a medication used to treat erectile dysfunction and pulmonary arterial hypertension.[3] It is unclear if it is effective for treating sexual dysfunction in women.[3] It is taken by mouth or injection into a vein.[3] Onset is typically within 20 minutes and lasts for about 2 hours.[3]



Side Effects

Common side effects include headaches, heartburn, and flushed skin.[3] Caution is advised in those with cardiovascular disease.[3] Rare but serious side effects include a prolonged erection that can lead to damage to the penis, vision problems, and hearing loss.[3] Sildenafil should not be taken by people on nitrates such as nitroglycerin (glycerin trinitrate), as this may result in a serious drop in blood pressure.[3]

Sildenafil acts by blocking phosphodiesterase 5 (PDE 5 ), an enzyme that promotes breakdown of cGMP, which regulates blood flow in the penis.[3] It requires sexual arousal, however, to work.[3] It also results in dilation of the blood vessels in the lungs.[3]