An inherited eye disease that affects the retina. You can take sildenafil with or without food. Condensation with 1-methylpiperazine. The best time to take sildenafil is about 1 hour before sexual activity, but you can take the medication any time from 4 hours to 30 minutes before sexual activity. This will increase the supply of blood to the lungs and reduce the workload of the heart. This can happen if you are sick with fever, diarrhea, or vomiting; sweat a lot; or do not drink enough liquids. You’ll soon start receiving the latest Mayo Clinic health information you requested in your inbox.Do not take sildenafil with any other product that contains sildenafil or other similar medications for erectile dysfunction-ED or pulmonary hypertension (such as tadalafil, .  · Description and Brand Names. Drug information provided by: Merative, Micromedex® US Brand Name. Revatio; Viagra; Descriptions. Sildenafil is used to treat . Sildenafil (Viagra). Tadalafil (Cialis). Vardenafil. These medicines are called PDE5 inhibitors. They enhance the effects of a chemical the body makes that relaxes .