<p>Care should be taken when administering Dutasteride to patients taking potent, chronic CYP3A4 inhibitors. Dutasteride does not inhibit the in vitro metabolism of model substrates for the major human cytochrome P450 isoenzymes (CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4) at a concentration of 1,000 ng/ml, 25 times greater than steady-state serum concentrations in humans. In vitro studies demonstrate that Dutasteride does not displace Warfarin, Diazepam, or Phenytoin from plasma protein binding sites, nor do these model compounds displace Dutasteride</p>