Sildenafil is a medication primarily used to treat erectile dysfunction (ED) in men. It works by increasing blood flow to the penis, helping to achieve and maintain an erection when sexually stimulated. Sildenafil is often sold under the brand name Viagra and is taken orally, usually about 30 minutes to an hour before sexual activity. In addition to treating ED, Sildenafil is also prescribed for pulmonary arterial hypertension (PAH), a condition that affects blood vessels in the lungs. By relaxing blood vessels, it helps improve exercise capacity and reduce symptoms in patients with PAH. Always consult a healthcare professional before using this medication.