Viagra

Sildenafil, commonly known as Viagra, is a medication used to treat erectile dysfunction, pulmonary arterial hypertension, and certain symptoms of secondary Raynaud's phenomenon. It is taken orally, intravenously, or sublingually and works by blocking phosphodiesterase 5, an enzyme that promotes breakdown of cGMP, which regulates blood flow. Common side effects include headaches, heartburn, and flushed skin, while rare but serious side effects include vision problems, hearing loss, and prolonged erection.learn more on wikipedia