Ethnicity and OPRM variant independently predict pain perception and patient-controlled analgesia usage for post-operative pain.
BACKGROUND
Morphine consumption can vary widely between individuals even for identical surgical procedures. As mu-opioid receptor (OPRM1) is known to modulate pain perception and mediate the analgesic effects of opioid compounds in the central nervous system, we examined the influence of two OPRM polymorphisms on acute post-operative pain and morphine usage in women undergoing elective caesarean delivery.


RESULTS
Data on self-reported pain scores and amount of total morphine use according to patient-controlled analgesia were collected from 994 women from the three main ethnic groups in Singapore. We found statistically significant association of the OPRM 118A>G with self-administered morphine during the first 24-hour postoperative period both in terms of total morphine (p = 1.7 x 10(-5)) and weight-adjusted morphine (p = 6.6 x 10(-5)). There was also significant association of this OPRM variant and time-averaged self-rated pain scores (p = 0.024). OPRM 118G homozygotes used more morphine and reported higher pain scores than 118A carriers. Other factors which influenced pain score and morphine usage include ethnicity, age and paying class.


CONCLUSIONS
Our results suggest that ethnicity and OPRM 118A>G genotype are independent and significant contributors to variation in pain perception and postoperative morphine use in patients undergoing cesarean delivery.
Tan
Ene-choo
EC
KK Research Centre, KK Women's and Children's Hospital, Singapore. tanec@bigfoot.com
Lim
Eileen C P
EC
Teo
Yik-ying
YY
Lim
Yvonne
Y
Law
Hai-yang
HY
Sia
Alex T
AT
D000328:Adult; D016058:Analgesia, Patient-Controlled; D005006:Ethnicity; D005260:Female; D005838:Genotype; D006801:Humans; D009020:Morphine / Q000627:therapeutic use; D010147:Pain Measurement; D010149:Postoperative Pain / Q000188:drug therapy* / Q000208:ethnology / Q000209:etiology* / Q000235:genetics; D010597:Pharmacogenetics; D020641:Polymorphism, Single Nucleotide; D011237:Predictive Value of Tests; D011247:Pregnancy; D017450:Receptors, Opioid, mu / Q000235:genetics*
C485764:OPRM1 protein, human; D017450:Receptors, Opioid, mu; D009020:Morphine