Viagra and other popular prescription medications for erectile dysfunction belong to a drug class known as PDE-5 inhibitors. They work by inhibiting the action of an enzyme called PDE-5, which breaks down another substance called cyclic AMP. Less cyclic AMP means blood vessels cannot relax and allow maximum blood flow in, which can make it difficult to have an erection. Viagra, Cialis, Levitra, and Staxyn inhibit PDE-5, allowing for higher levels of cyclic AMP, so blood vessels can open fully and allow sufficient blood flow.
Some erectile dysfunction medications must be timed more carefully than others.
By themselves, the drugs do not “cause” erections, but in the presence of sexual stimulation, they make it easier to get and maintain an erection, and make erections stronger. But the different drugs are all formulated slightly differently, so there are subtle (and sometimes not-so-subtle) differences in their effects.
How you take the drugs and when you take them can influence how well they work. Here are some frequently asked questions about the timing of use of medications for erectile dysfunction.