What are PDE5 Inhibitors?
The most commonly used medicines to treat erectile dysfunction are from a class of medicines known as the PDE5 Inhibitors.
During sexual stimulation, the release of nitric oxide into the corpus cavernosum produces erections. Nitric oxide then activates the enzyme guanylate cyclase, which results in increased levels of cyclic guanosine monophosphate (cGMP). cGMP causes smooth muscle relaxation in the corpus cavernosum and so allows the inflow of blood.
cGMP specific phosphodiesterase type 5 (PDE5) is an enzyme present in corpus cavernosum, responsible for degradation of cGMP and so reversing the erectile effect it creates. If the PDE5 is inhibited, then the cGMP will persist for longer and levels in the tissues increase. This in turn increases the relaxation of the arteries and the blood flow – so increasing the erection.