In vitro activity: Vardenafil specifically inhibits the hydrolysis of cGMP by PDE5 with an IC50 of 0.7 nM (6.6 nM). Vardenafil significantly enhances the SNP-induced relaxation of human trabecular smooth muscle at 3 nM (10 nM). Vardenafil also significantly potentiates both ACh-induced and transmural electrical stimulation-induced relaxation of trabecular smooth muscle. Vardenafil (100 mM) increases cyclic GMP levels in rat hippocampal slices. Vardenafil, tadalafil, and Sildenafil each competitively inhibit cGMP hydrolysis by phosphodiesterase-5 (PDE5), thereby fostering cGMP accumulation and relaxation of vascular smooth muscle.

Kinase Assay: Vardenafil specifically inhibited the hydrolysis of cGMP by PDE5 with an IC50 of 0.7 nM (6.6 nM). In contrast, the IC50 of vardenafil for PDE1 was 180 nM; for PDE6, 11 nM; for PDE2, PDE3 and PDE4, more than 1000 nM. Relative to PDE5, the ratios of the IC50 for PDE1 were 257 (60), for PDE6 16 (7.4).

Cell Assay: Vardenafil significantly enhanced the SNP-induced relaxation of human trabecular smooth muscle at 3 nM (10 nM). Vardenafil also significantly potentiated both ACh-induced and transmural electrical stimulation-induced relaxation of trabecular smooth muscle.