['Previous reports have suggested that polymorphism of the opioid receptor A118G affects the efficacy of opioid analgesia. The aim of this study was to investigate whether such polymorphism contributed to variability in epidural mixture (sufentanil plus ropivacaine) requirements through patient-controlled epidural analgesia (PCEA) after cesarean section.', 'One hundred eighty consenting women undergoing elective cesarean delivery were enrolled in the study. Patients received sufentanil and ropivacaine for pain control after surgery. Sufentanil (50 mcg) diluted with 0.2% ropivacaine in a total volume of 100 mL was administered by PCEA with a background infusion rate of 2 mL/h and a pump program set to deliver 0.5-mL boluses with a lockout time of 15 minutes. The analgesic effect and adverse effects were measured with rating scales. The total consumption of the epidural mixture in the first 24 hours postoperatively was recorded. Blood samples were genotyped to classify patients into 3 groups according to A118G polymorphism.', 'Of 161 patients included in the analysis, 63 were homozygous (AA), 81 were heterozygous (AG), and 17 were homozygous (GG) for the A118G polymorphism. No difference was observed among groups in the consumption of the epidural mixture within the first 24 hours postoperatively (P = 0.3). Satisfaction with analgesia, pain scores, and adverse effects were similar among the groups.'] Does opioid receptor A118G polymorphism affect the consumption of sufentanil and ropivacaine by patient-controlled epidural analgesia after cesarean section?