Levitra is used for reating erectile dysfunction (ED). It may also be used for other conditions as determined by your doctor. Do not take Levitra more than once a day. Allow 24 hours to pass between doses. Contact your doctor or seek emergency medical attention if your erection is painful or lasts longer than 4 hours. A prolonged erection (priapism) can damage the penis. Levitra is a phosphodiesterase type 5 (PDE5) inhibitor. It works by helping to increase blood flow into the penis during sexual stimulation. This helps you to achieve and maintain an erection.