The drugs used to treat erectile dysfunction are known as PDE-5 inhibitors. A substance called phosphodiesterase type 5 (PDE-5) degrades a circulating compound called cyclic GMP, which is present in the smooth muscle cells lining the blood vessels that supply the penis. By inhibiting the action of PDE-5, more cyclic GMP is available, so conditions are more favorable for an erection in the presence of sexual stimulation.
PDE-5 inhibitors work by mimicking, to an extent, the positive circulatory effects of regular exercise.
Viagra, Levitra, Staxyn (a quick-dissolve formulation of Levitra), and Cialis are good at inhibiting PDE-5, but they’re not 100% selective for that substance, particularly at higher dosages. For example, Viagra, in addition to inhibiting PDE-5, also inhibits PDE-6 and PDE-9.
In fact, it is the inhibition of PDE-6, which is present in the retina of the eye, that is believed to be responsible for vision changes that some men report as a side effect of Viagra. Cialis, in addition to inhibiting PDE-5, also inhibits PDE-11.
All this is a roundabout way of saying that PDE-5 inhibitors are similar, but not identical in action, and the user’s physiology, and how the drugs are taken can have a subtle effect on how well they work and how long they take to be effective. Food can affect the action of some, but not all erectile dysfunction drugs. Here are some frequently asked questions about taking erectile dysfunction medication with food.