Tadalafil (IC-351) is a carboline-based compound with vasodilatory activity. Tadalafil selectively inhibits the cyclic guanosine monophosphate (cGMP)-specific type 5 phosphodiesterase- (PDE-5)-mediated degradation of cGMP, which is found in the smooth muscle of the corpus cavernosa and corpus spongiosum of the penis. Inhibition of cGMP degradation by tadalafil results in prolonged muscle relaxation, vasodilation, and blood engorgement of the corpus cavernosa, and, so, prolonged penile erection.

PDE5:1.8 nM

Tadalafil（2或10 mg/kg）对神经功能恢复具有显著促进作用,还能使脑血管密度和BrdU阳性血管内皮细胞的百分比增加.在假手术组大鼠中,Tadalafil（2 mg/kg）几乎完全恢复阴茎组织氧化且阻断神经切断诱导的增加,还能大幅提高阴茎组织部分的肌肉/纤维比例. 作用于大鼠大脑时,Tadalafil使cGMP含量选择性增加,而非环磷酸腺苷.Tadalafil降低大鼠体内凋亡细胞的数量,提高激酶Akt和细胞外信号调节激酶1/2的磷酸化（两种生存相关激酶）.

作用于人肝细胞时,Tadalafil（1 mM）刻使CYP3A蛋白表达上升。Tadalafil可与5型磷酸二酯酶结合（KD：2.4 nM）,该结合受cGMP 刺激。