Table 4.

In vitro inhibition of sildenafil metabolism by CYP3A4 inhibitors. The values are means ± s.d. of triplicate determinations in microsomes prepared from a pool of four human lvers.

Inhibitor	IC50 (µm)
Itraconazole	0.010 ± 0.001
Ketoconazole	0.043 ± 0.008
Indinavir	0.254 ± 0.073
Nelfinavir	0.611 ± 0.113
Saquinavir	∼5
Ritonavir	0.003 ± 0.0003