Should I see a specialist? 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. You can take this medicine with or without food 30 minutes before sex, depending on the dose. What’s the best treatment? Follow your doctor’s orders or the directions on the label. You can take this medicine with or without food 30 minutes before sex, depending on the dose. The dosages might also be unknown, or they might have been contaminated during formulation.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 often last for 4 to 5 hours. It might work longer if you have mild to moderate erectile dysfunction. Vardenafil. It’s a prescription drug that’s used in adult males* with ED. With ED, you have trouble getting or keeping an erection. Viagra treats ED by increasing the amount of blood flow to your penis. Sildenafil (Viagra) is used to treat erectile dysfunction (impotence; inability to get or keep an erection) in men. 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 hypertension (PAH; high blood pressure in the vessels carrying blood to the lungs, causing shortness of.