Viagra contains the active ingredient Sildenafil, which is also available in an unbranded generic form. Payment options: Consider how you’d like to pay. Cialis tadalafil : This ED medication works with the same principle as Viagra, but lasts up to 36 hours. These medicines all work well for ED. In some cases, online ED providers accept health insurance. There are many safe, reliable online services offering ED prescriptions. Some examples of nitrates are nitroglycerin Nitro-Dur, Nitrostat, others , isosorbide mononitrate Monoket and isosorbide dinitrate Bidil.Drug Images What is Viagra? Viagra is a brand-name prescription drug that’s approved to treat erectile dysfunction (ED). With ED, you’re unable to have or maintain an erection. . Medical Consultation Required: Yes Medications Prescribed: Viagra, Cialis, sildenafil, tadalafil Generic offered: Yes Why We Chose It. 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 .