Table 5.

Comparison of IC₅₀ Values of PDE-5 Inhibitors

	IC50 Value, nM
PDE Family	Sildenafil	Vardenafil	Tadalafil
PDE-1	280	69	<30,000
PDE-2	68,000	6200	>30,000
PDE-3	16,200	4000	>30,000
PDE-4	7200	4000	>30,000
PDE-5	0.5–4.0	0.1–0.7	0.9–6.7
PDE-6	38	157	780
PDE-7	21,000	<30,000	> 100,000
PDE-8	29,800	>30,000	> 100,000
PDE-9	2610	580	> 100,000
PDE-10	9800	3000	> 100,000
PDE-11	2730	162	37

IC₅₀, concentration needed to inhibit 50% of PDE activity; PDE, phosphodiesterase.

Data from Corbin JD, Francis SH. Int J Clin Pract. 2002;56:453–459⁴⁴; Bischoff E et al. Int J Impot Res. 2001;13(suppl 4):S41⁴⁵; Eardley I et al. Int J Clin Pract. 2002;56:300–304⁴⁶; Omrod D et al.Drugs Aging. 2002;19:217–227.⁴⁷