In turn, neither warfarin nor diazepam altered the binding of quetiapine. Quetiapine is extensively metabolized by the liver. In vitro studies using human liver microsomes revealed that the cytochrome P450 3A4 isoenzyme is involved in the metabolism of quetiapine to its major, but inactive, sulfoxide metabolite. There is no gender effect on the pharmacokinetics of quetiapine. There is no race effect on the pharmacokinetics of quetiapine.
Smoking has no effect on the oral clearance of quetiapine.
Dosage adjustment is therefore not needed in these patients. In two of the 8 hepatically impaired patients, AUC and C max were 3-times higher than those observed typically in healthy subjects. Since quetiapine is extensively metabolized by the liver , higher plasma levels are expected in the hepatically impaired population, and dosage adjustment may be needed. P450 1A2, 2C9, 2C19, 2D6 and 3A4. Quetiapine oral clearance is induced by the prototype cytochrome P450 3A4 inducer, phenytoin.