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. Viagra is approved for this use in males ages 18 years and older.

Viagra contains the drug sildenafil. It belongs to a class of drugs called phosphodiesterase type 5 (PDE5) inhibitors. (A class of drugs is a group of medications that act in a similar way.) Viagra works by increasing blood flow to your penis, which helps you have and keep an erection. But this drug only works if you’re sexually aroused.