The influence of DNA polymorphism of multidrug resistant 1 (MDR1) on the effect of midazolam pretreatment in children

BACKGROUND Patients showed a different response following intravenous midazolam injection. Some children showed irritability or were not sedated by midazolam. We hypothesized that there may be genetic variations of the MDR1 gene, based on the response to midazolam. METHODS One hundred and ninety-three pediatric patients were recruited in this study. Midazolam (0.1 mg/kg) was injected intravenously before surgery. Anxiety score (activity, vocalizations, emotional expressivity, state of apparent arousal) was checked before and 5 minutes after midazolam injection. In addition, other manifestations after midazolam injection were recorded. After anesthesia, 2 ml of blood was sampled. Children were genotyped MDR1. Haplotype was analyzed using the software package PHASE, version 2.0. RESULTS The observed frequencies of MDR1 haplotype of TTT, TGC, CAC, CGC were 0.334, 0.205, 0.182 and 0.225, respectively. There was no significant correlation between the response of midazolam and the MDR1 haplotype of TTT, TGC, CAC or CGC (P = 0.98). CONCLUSIONS Genotyping of MDR1 may not be related to the response of midazolam in children.