Functional polymorphisms of the cytochrome P450 1A2 (CYP1A2) gene and prolonged QTc interval in schizophrenia

CYP1A2 is an important inducible enzyme involved in the metabolism of antipsychotics. This study examined two functional polymorphisms in the gene as potential markers in predicting prolongation of QTc interval in patients treated with antipsychotics. QT intervals were measured by 12-lead electrocardiography (ECG) for patients with a DSM-IV diagnosis of schizophrenia. Genomic DNA extracted from venous blood were genotyped for the two polymorphisms by PCR-RFLP. Statistically significant result for CYP1A2 ⁎ 1F was noted for all patients receiving chlorpromazine equivalent doses of above 300   mg and also for a further subgroup on antipsychotics known to be CYP1A2 substrates (p = 0.007, mean QTc in ms for A/A: 395.5 ± 15.1, A/C: 425.7 ± 25.1, C/C: 427.3 ± 20.7). For CYP1A2 ⁎ 1C, there was no statistically significant association between genotypes and mean QTc interval. Overall, there was a trend of those with the C allele of the CYP1A2 ⁎ 1F polymorphism having longer QTc intervals. The results of this study suggest that the CYP1A2 ⁎ 1F polymorphism may contribute to the risk of developing prolonged QT-interval in patients who are treated with higher doses of antipsychotics.