​Levitra is in a class of medications called phosphodiesterase 5 (PDE5) inhibitors that work by increasing blood flow to the penis during sexual stimulation to help men get and maintain an erection. Cialis does not cure ED or increase sexual desire. It does not prevent pregnancy or protect against sexually transmitted diseases. Levitra can be taken once daily, and you can attempt sex any time between doses. It can also be taken as needed, approximately 30 minutes before sexual activity or as directed by your doctor. Do not take more or less than what your doctor prescribes.