Ask your pharmacist or doctor for a copy of the manufacturer’s information for the patient. When a man is sexually stimulated, his body’s normal response is to increase blood flow to his penis to produce an erection. Sildenafil works on the PDE5 enzyme in the lungs to relax the blood vessels. From Mayo Clinic to your inbox Sign up for free and stay up to date on research advancements, health tips, current health topics, and expertise on managing health. Take sildenafil at around the same times every day. If you are a Mayo Clinic patient, this could include protected health information. If we combine this information with your protected health information, we will treat all of that information as protected health information and will only use or disclose that information as set forth in our notice of privacy practices.Sildenafil is a prescription drug. It comes in the form of a tablet and suspension (liquid). Both are taken by mouth. It also comes in an intravenous (IV) form, which is only given by a doctor. Find patient medical information for sildenafil oral on MD including its uses, side effects and safety, interactions, pictures, warnings and user ratings. (including prescription drugs.  · Medically reviewed by test1.ru Last updated on Applies to the following strengths: 10 mg/mL; 10 mg/ mL; 20 mg; 25 mg; 50 mg; mg Usual Adult Dose for: Erectile Dysfunction Pulmonary Hypertension Usual Geriatric Dose for: Erectile Dysfunction Additional dosage information: Renal .