Viagra, Cialis and Levitra are oral drugs used successfully for treatment of erectile dysfunction (ED). They work by enhancing the effects of nitric oxide, a mediator that relaxes smooth muscles in the penis, which leads to dilatation of the blood vessels, thus helping the patient achieve and maintain an erection. These medications cause erections only during sexual excitement. They can be taken as often as once a day.
Generic Viagra, Cialis and Levitra is a generic version of the same potent medication available at a much lower price.