Sildenafil

Lore & Background

Sildenafil acts by blocking phosphodiesterase 5 (PDE5), an enzyme that promotes breakdown of cGMP, which regulates blood flow in the penis. It requires sexual arousal to work and does not by itself cause or increase sexual arousal. It also results in dilation of blood vessels in the lungs. Common side effects include headaches, heartburn, and flushed skin. Rare but serious side effects include vision problems, hearing loss, and prolonged erection (priapism) that can lead to damage to the penis. Sildenafil should not be taken by people on nitric oxide donors such as nitroglycerin, as this may result in a serious drop in blood pressure.

Reader's Guide

Sildenafil's primary indication is erectile dysfunction, and it is now a standard treatment, including for males with diabetes mellitus. It also improves some markers of disease in pulmonary arterial hypertension, though it does not appear to affect the risk of death or serious side effects. Off-label, it is used for secondary Raynaud's phenomenon to alleviate vasospasm and treat severe ischemia and ulcers. Its efficacy for sexual dysfunction in females is unclear. In 2023, it was the 151st most commonly prescribed medication in the United States, with more than 3 million prescriptions. It is available as a generic medication and, in the United Kingdom, as a pharmacy medicine. Recreational use is noted among young adults and users of illegal drugs, often mixed with other substances, which can be dangerous. The drug has also been studied for altitude sickness and jet lag in hamsters, but its overall efficacy for these uses is not clear.

Did You Know?

• It can be taken orally, intravenously, or sublingually.
• A rare but serious side effect is priapism, a prolonged erection that can damage the penis.
• The 2007 Ig Nobel Prize in aviation was awarded for discovering that sildenafil helps treat jet lag recovery in hamsters.