[Human µ-opioid receptor A118G polymorphism affects epidural patient-controlled analgesia with fentanyl].

OBJECTIVE: To investigate whether A118G single nucleotide polymorphisms of the µ-opioid receptor (OPRM1) affects epidural patient-controlled analgesia with fentanyl after caesarean section.
METHODS: A total of 100 pregnant women (ASA class I or II) scheduled for elective caesarean section were enrolled in this study. All the patients received spinal-epidural anesthesia and were screened for blood A118G polymorphism. Epidural patient-controlled analgesia with fentanyl was provided postoperatively. The pain scores, incidence of nausea and vomiting, and total self-administered epidural fentanyl dose within 48 h postoperatively were recorded.
RESULTS: Ninety-six patients were finally included in this study. The percentages of the genotypes AA, AG, and GG were 36.5% (35 cases), 46.9% (45 cases), and 16.7% (16 cases), respectively. At 12 and 24 h postoperatively, the pain scores and the total fentanyl dose administered were significantly higher in group GG than in groups AA and AG.
CONCLUSION: A118G single nucleotide polymorphism affects pain relief and total fentanyl dose administered in epidural patient-controlled analgesia after caesarean section. G118 homozygotes have a poorer response to fentanyl than A118 homozygotes or heterozygotes.