You can take this medicine with or without food 30 minutes before sex, depending on the dose. Do not press on the plunger of the syringe. Your doctor or other health care professional can recommend one for you based on these factors, other health conditions you have and any other medicines you take. When hypertension occurs in the lungs, the heart must work harder to pump enough blood through the lungs. By controlling the enzyme, sildenafil helps to maintain an erection after the penis is stroked. Do not take a double dose to make up for a missed one. If you are a Mayo Clinic patient, this could include protected health information. · Description and Brand Names. Drug information provided by: Merative, Micromedex ®. US Brand Name. Revatio. Viagra. Descriptions. Sildenafil is used to . Viagra basics. The active drug in Viagra is sildenafil. It belongs to a group of drugs called phosphodiesterase-5 inhibitors. Viagra comes as tablets you take by . 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, .