Study of the OPRM1 A118G genetic polymorphism associated with postoperative nausea and vomiting induced by fentanyl intravenous analgesia.

BACKGROUND

Genetic polymorphisms of the μ-opioid receptor gene OPRM1 A118G have been shown to influence opioid efficacy. The association of the OPRM1 A118G genetic polymorphism with side effects, such as nausea and vomiting, caused by opioids during analgesia has not been well-represented by the literature . This study aimed to investigate whether the genetic polymorphism of OPRM1 A118G contributed to the variability in nausea and vomiting during fentanyl analgesia in patients undergoing total abdominal hysterectomy or myomectomy.

METHODS

One hundred sixty-five women, of Han nationality, aged 20-50 yrs, of ASA I or II, and scheduled for elective total abdominal hysterectomy or myomectomy under general anesthesia were enrolled. Intravenous fentanyl, patient-controlled analgesia was provided postoperatively for pain control. The presence and scores of postoperative nausea and vomiting for 24 hours were recorded and measured using rating scales. Pain was measured with a visual analog scale, and fentanyl consumption over 24 hours was recorded, as well. Genotyping of the A118G allele was conducted by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), and patients were divided into three groups according to their genotype.

RESULTS

The frequency of the A118G allele was 32.4% for the patients in this study. Patients homozygous for 118G required more fentanyl to achieve adequate pain relief compared with the other two patient groups (patients homozygous for 118A and heterozygous). However, there were no statistically significant differences among the frequencies and scores of nausea and vomiting.

CONCLUSION

OPRM1 A118G has no effect on the individual variation of postoperative nausea and vomiting, the side effects of fentanyl analgesia, in Chinese women undergoing gynecologic surgery.