['We attempted to clarify the influence of polymorphisms of nuclear receptors on carbamazepine therapy.', 'The common polymorphisms of nuclear receptors--a tentative pregnane X receptor (PXR)*1B, hepatocyte nuclear factor 4α (HNF4α) rs2071197 (c.115+308G>A), and cytochrome P450 3A5*3 polymorphisms--were genotyped in 168 Japanese patients with epilepsy. The associations of these polymorphisms with the disposition, clinical efficacy, and incidence of adverse effects of carbamazepine treatment were retrospectively investigated in 104 patients treated with carbamazepine alone. The associations with disposition were also assessed in 64 patients treated with carbamazepine and other antiepileptic drugs, which constituted the internal replication group, and in the combined 168 patients.', 'Neither polymorphism alone affected the carbamazepine disposition, but a significant interactive effect of PXR*1B and HNF4α rs2071197 polymorphisms on the concentration-to-dose (C/D) ratios was observed (P=0.027). The C/D ratios among patients with the HNF4α G/G genotype were higher in PXR*1B carriers than in PXR*1B noncarriers, which was confirmed in the internal replication and combined groups. In patients with the HNF4α G/G genotype, the rate of freedom from seizures until 3 months after starting carbamazepine therapy was significantly greater and the time required to reach the dose required for seizure freedom was shorter in PXR*1B carriers than in PXR*1B noncarriers.'] Are pregnane X receptor and hepatocyte nuclear factor 4α polymorphisms cooperatively associated with carbamazepine autoinduction?