PDE5 inhibitors, which have been certified for the treatment of erectile dysfunction, pulmonary hypertension, LUTSs associated with BPH, and penile rehabilitation after radical prostatectomy, are all taken by mouth, absorbed in the small intestine, and metabolized in the liver via CYP3A pathway [46]. The gene discussed is CYP3A4; the disease is pulmonary arterial hypertension.