Viagra is a medication for erectile dysfunction (ED) that works by improving blood flow to the penis through the inhibition of an enzyme called PDE5. This helps men achieve and maintain a firmer erection.

Taken orally in tablet form, Viagra typically begins working within 30–60 minutes and remains effective for around 4–6 hours. It does not cause arousal on its own—you’ll only get an erection when you’re sexually stimulated.

Viagra is also available in an unbranded form called sildenafil. Containing the same active ingredient, it is equally effective as branded Viagra but can cost up to 80% less.