Do not take a double dose to make up for a missed one. If you are taking sildenafil to treat erectile dysfunction, follow your doctor’s directions and the guidelines in this paragraph. You’ll soon start receiving the latest Mayo Clinic health information you requested in your inbox. This can happen if you are sick with fever, diarrhea, or vomiting; sweat a lot; or do not drink enough liquids. What special dietary instructions should I follow?Drugs & Medications Viagra Viagra – Uses, Side Effects, and More Generic Name (S): sildenafil Uses Sildenafil is used to treat male sexual function problems (impotence or . Sildenafil (Liqrev, Revatio) is used to improve the ability to exercise in adults (Liqrev, Revatio) and children 1 year of age and older (Revatio) with pulmonary arterial . Sildenafil (Viagra). This medicine works best when you take it on an empty stomach an hour before sex. The body takes longer to absorb it after a high-fat meal or alcohol. Its effects .