Knowing whether or not you have insurance to cover the medication will make a difference in how you obtain it. Its effects often last for 4 to 5 hours. Medicines that you take by mouth are called oral medicines. Then, you get access to the pills for a whole month. They’re often the first line of treatment for trouble getting or keeping an erection, called erectile dysfunction ED.Factors affecting dosage. How to take. Missed dose. Overdose. Takeaway. Drug Images. Viagra treats erectile dysfunction (ED) in adults. It’s usually taken about 1 hour before . Generic name: sildenafil (oral) [ sil-DEN-a-fil ] Brand names: Revatio, Viagra. Drug class: Impotence agents. Medically reviewed by Sophia Entringer, PharmD. Last updated on . AdDon’t go to the pharmacy without checking prices at GoodRx® first. No commitment or fees. Find the lowest price in your neighborhood & use our free coupons to save up to 80%5-Star Reviews · No Credit Card Required · Over 70k Pharmacies””GoodRx can help you save, whether you have insurance or not.”” – Patch.