Association between opioid receptor gene polymorphism and postoperative pain response in Koreans

ABSTRACT

BACKGROUND: The objective of this study was to investigate the association between A118G single nucleotide polymorphism (SNP) of human micro-opioid receptor (OPRM1) gene and the postoperative pain response in Korean patients undergoing thyroidectomy. METHODS: Fifty two adult patients undergoing thyroidectomy were enrolled in this study. Their blood samples were genotyped for the A118G polymorphism. Pain intensity was assessed by a verbal numerical rating scale (VNRS) at postanesthesia care unit, postoperative 6, 24, and 48 hours. Mechanical pain threshold was assessed using electronic von Frey preoperatively and repeated at postoperative 24 and 48 hours on the forearm and periincisional regions. RESULTS: Of the 50 patients, 23 patients were A118 homozygous (AA), 19 patients were heterozygous (AG), and 8 patients were 118G homozygous (GG). The VNRS score was higher in patients with GG genotype than other genotypes at PACU (P < 0.05). Mechanical pain thresholds on the forearm and periincisional area were decreased at postoperative 24 and 48 hours from the preoperative values in all genotypes (P < 0.05). However, the changes in pain thresholds were similar among the genotypes. CONCLUSIONS: A118G SNP of OPRM1 gene is associated with inter-individual difference in immediate postoperative pain score in Korean population.