In addition, N-desmethyl metabolite AUC and C max values had been considerably elevated 200% and 79%, respectively, in patients with severe renal impairment compared to patients with normal renal operate. Sildenafil is a weak inhibitor of the cytochrome P450 isoforms 1A2, 2C9, 2C19, 2D6, 2E1 and 3A (IC 50 better