Avanafil is used to treat erectile dysfunction (impotence). Avanafil should not be taken by a woman or a child. Avanafil may also be used for purposes not listed in this medication guide.Avanafil acts by inhibiting a specific phosphodiesterase type 5 enzyme found in various body tissues, primarily in the corpus cavernosum penis. Other similar drugs are sildenafil, tadalafil and vardenafil. The advantage of avanafil is that it has very fast onset of action compared with other PDE5 inhibitors.