Sildenafil, sold under the brand name Viagra among others, is a medication used to treat erectile dysfunction and pulmonary arterial hypertension. It is unclear if it is effective for treating sexual dysfunction in women. It is taken by mouth or injection into a vein. Onset is typically within 20 minutes and lasts for about 2 hours.
Headaches, heartburn, and flushed skin are typical side-effects. For those with cardiovascular disease, caution is recommended. A prolonged erection that can lead to damage to the penis, vision issues, and hearing loss are uncommon but severe side effects. People with nitrates such as nitroglycerin (glycerin trinitrate) should not take sildenafil, as this may result in a significant drop in blood pressure.
By blocking phosphodiesterase 5 ( PDE5), an enzyme that promotes cGMP breakdown that controls blood flow in the penis, sildenafil acts. However, it needs sexual arousal to function. It also results in the blood vessels in the lungs being dilated.
When looking for a cure for heart-related chest pain, Pfizer originally discovered the drug in 1989. It was approved in the United States and Europe for medical use in 1998. In 2017, with more than two million prescriptions, it was the 217th most widely prescribed drug in the United States. In 2017, after Pfizer’s last patents expired, it became available as a generic drug. It is available over the counter in the United Kingdom.