The body takes longer to absorb it after a high-fat meal or alcohol. The following nonprescription or herbal products may interact with sildenafil: cimetidine Tagamet HB , St. Do not stop taking sildenafil without talking to your doctor. Take sildenafil at around the same times every day. By controlling the enzyme, sildenafil helps to maintain an erection after the penis is stroked.Do not take Viagra if you are also using a nitrate drug for chest pain or heart problems, including nitroglycerin, isosorbide dinitrate, isosorbide mononitrate, and some . No, you should not take Viagra if you don’t have ED. Viagra is a prescription medication that can have serious side effects. And it’s approved only to treat ED, not to be used recreationally. If you have erectile dysfunction (ED), your doctor may recommend that you take Viagra. It’s a prescription drug that’s used in adult males* with ED. With ED, you have trouble .