PDE5A and pulmonary arterial hypertension: Thus, pharmacological inhibition of PDE5A activity is in clinical application for treatment of erectile dysfunction and pulmonary arterial hypertension (PAH) using 8 (sildenafil, ViagraTM), 9 (vardenafil, LevitraTM), tadalafil (CialisTM), and avanafil (StendraTM) [9,20,32,88,89,90].