title: Effect of μ-opioid receptor A118G polymorphism on the ED50 of epidural sufentanil for labor analgesia.
abstract: BACKGROUND
  A common polymorphism of the μ-opioid receptor gene (OPRM1, p.118A/G), which has been shown to effect the response to neuraxial opioids, occurs in 30% of Caucasian women. This double-blind up-down sequential allocation study was designed to examine the effect of p.118A/G on the ED50 of epidural sufentanil for labor analgesia.
  
  
  METHODS
  Nulliparous women were recruited at 35 weeks of gestation (n=77) and genotyped for p.118A/G. Those subsequently requesting epidural labor analgesia were enrolled. Each woman received epidural sufentanil diluted with 0.9% saline to a volume of 5 mL. The initial sufentanil dose was 21 μg, with subsequent doses determined by the response of the previous patient (testing interval 1 μg). Efficacy was accepted if the visual analogue score decreased to <10mm on a 100-mm scale within 30 min of drug administration.
  
  
  RESULTS
  Twenty patients were excluded, leaving 57 women from whom data were analyzed: 33 in Group A (wild-type A118 homozygotes) and 24 in Group G (heterozygotes and homozygotes G118). The ED50 for epidural sufentanil was 25.2 μg in Group A (95% CI 23.2-26.4) and 20.2 μg in Group G (95% CI 14.2-23.6) (P=0.03). The potency ratio for epidural sufentanil in Group G compared to Group A was 1.25 (95% CI 1.00-1.64).
  
  
  CONCLUSIONS
  Women carrying the variant allele of p.118A/G of OPRM1 (G118) had a lower ED50 for epidural sufentanil given for early labor analgesia than women homozygous for the wild-type allele.
authors.affiliation: Department of Anesthesiology, Città di Roma Hospital, Rome, Italy. michelaca.mc@gmail.com
authors.forename: M
authors.initials: M
authors.lastname: Camorcia
authors.forename: G
authors.initials: G
authors.lastname: Capogna
authors.forename: S
authors.initials: S
authors.lastname: Stirparo
authors.forename: C
authors.initials: C
authors.lastname: Berritta
authors.forename: J L
authors.initials: JL
authors.lastname: Blouin
authors.forename: R
authors.initials: R
authors.lastname: Landau
mesh_terms: D000328:Adult; D015360:Analgesia, Epidural; D016362:Analgesia, Obstetrical; D000701:Analgesics, Opioid / Q000008:administration & dosage*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D020641:Polymorphism, Single Nucleotide; D011247:Pregnancy; D017450:Receptors, Opioid, mu / Q000235:genetics*; D017409:Sufentanil / Q000008:administration & dosage*
chemical_list: D000701:Analgesics, Opioid; D017450:Receptors, Opioid, mu; D017409:Sufentanil