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. 2001 Mar;51(3):239–248. doi: 10.1046/j.1365-2125.2001.00318.x

Table 5.

In vitro inhibition of CYP activities by sildenafil. The values are mean ± s.d. of triplicate determinations in microsomes prepared from a pool of four human livers.

Isozyme Activity measured IC50m)
CYP1A2 Phenacetin O-deethylase > 300
CYP2C9 Phenytoin 4-hydroxylase 150 ± 23
CYP2C19 (S)-mephenytoin 4-hydroxylase > 300
CYP2D6 Bufuralol 1′-hydroxylase > 300
CYP2E1 Chlorzoxazone 6-hydroxylase > 300
CYP3A4 Felodipine oxidase > 300
Testosterone 6β-hydroxylase > 300
Terfenadine hydroxylase 105 ± 7