Avanafil is a PDE5 inhibitor approved for erectile dysfunction by FDA and by EMA. Avanafil is known by the trademark names Stendra and Spedra and was developed by Vivus Inc. Avanafil selectively inhibits PDE5, thus inhibiting the degradation of cyclic guanosine monophosphate (cGMP) found in the smooth muscle of the corpus cavernosa of the penis. The physiologic mechanism of erection of the penis involves release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation. NO then activates the enzyme guanylate cyclase, which results in increased levels of cGMP, producing smooth muscle relaxation in the corpus cavernosum and allowing inflow of blood. Avanafil has no direct relaxant effect on isolated human corpus cavernosum, but enhances the effect of NO by inhibiting PDE5, which is responsible for degradation of cGMP in the corpus cavernosum. Because sexual stimulation is required to initiate the local release of nitric oxide, the inhibition of PDE5 has noeffect in the absence of sexual stimulation. The advantage of avanafil is that it has very fast onset of action compared with other PDE5 inhibitors. It is absorbed quickly, reaching a maximum concentration in about 30–45 minutes. About two-thirds of the participants were able to engage in sexual activity within 15 minutes.