Sildenafil comes as a tablet and suspension liquid to take by mouth. What special precautions should I follow? You’ll also need to fill out a medical questionnaire with answers about your medical history, current medications, and lifestyle habits. Most erectile dysfunction medications belong to the drug class known as PDE5 inhibitors , which help relax the muscles and increase blood flow to allow for a full erection. They’re often the first line of treatment for trouble getting or keeping an erection, called erectile dysfunction ED. Oral ED medicines might not work or might be dangerous if you also take any of the following: Nitrate medicines.You’ll typically take Viagra about 1 hour before sex. You can take the drug 30 minutes to 4 hours before you anticipate sexual activity. Based on how well you respond to this . 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 . Medications Prescribed: Viagra, Cialis, sildenafil, tadalafil Generic offered: Yes Why We Chose It.