They’re often the first line of treatment for trouble getting or keeping an erection, called erectile dysfunction ED. But, you should still see your doctor to discuss other health issues. Vardenafil usually works for 4 to 5 hours. These small differences affect the way each medication works, such as how quickly it takes effect and wears off, and the possible side effects. Oral medicines for ED usually work well and cause few side effects. This medicine also works best when you take it an hour before sex on an empty stomach. These medicines are called PDE5 inhibitors.If you do buy medicines over the internet: Check to see if an online pharmacy is legitimate. Never order medicines from an online pharmacy that doesn’t . 1. It Targets the Problem and Works Quickly. Being a topical means MED targets your penis directly and offers a “quick onset of action,” Dr. Pearlman Missing: walgreens. Is there an over-the-counter Viagra? Viagra is only available with a prescription in the United States, Canada, and most other countries. Viagra is sold under .