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Influence of OPRM1 Polymorphism on Postoperative Pain After Intrathecal Morphine Administration in Italian Patients Undergoing Elective Cesarean Section

Pettini, Eleonora MD*; Micaglio, Massimo MD; Bitossi, Ubaldo MD; De Gaudio, Angelo R. MD*; Degl’Innocenti, Duccio R. MD*; Tofani, Lorenzo PhD; Limatola, Vittorio MD; Adembri, Chiara MD*; Di Filippo, Alessandro MD*

doi: 10.1097/AJP.0000000000000520
Original Articles

Objectives: The aim of this prospective observational study was to evaluate the influence of OPRM1 polymorphism on the analgesic efficacy (including visual analog scale [VAS] scores and requirement for rescue analgesia) of a standard dose of intrathecal morphine.

Materials and Methods: An Italian cohort of 63 parturients, scheduled for elective cesarean section at a tertiary University Hospital, received spinal anesthesia with hyperbaric bupivacaine and morphine 100 mcg. For the first 48 hours in the postoperative period the patients received acetaminophen 1 g IV q6hr. Incident pain was treated with ketorolac 30 mg IV. Every 6 hours the following parameters were registered: VAS at rest, VAS during movements, postoperative nausea and vomiting, pruritus, and rescue analgesic medications requirements. Age and anthropometric data, number of pregnancies, educational level, OPRM1 genotype, were also obtained.

Results: Of the 63 patients enrolled, 45 (71%) were homozygous genotype A/A (118A group), whereas 18 carried the G variants of OPRM1 (A/G or G/G) (118G group). No significant differences in analgesic rescue doses’ administration and in incidence of moderate/severe postoperative pain (VAS>3) between the 2 groups were observed. Pruritus was more frequent in the 118A group than in the 118G group in the first 24 hours of the postoperative period.

Discussion: In the Italian population participating in this study there was a different incidence of pruritus in the postcesarean period in response to intrathecal opioids related to OPRM1 gene polymorphism, but not of postoperative pain.

*Department of Health Sciences, Section of Anaesthesia, Intensive Care and Pain Therapy

Department of Neurosciences, Psychology, Drug Research and Child Health, University of Florence

Department of Anaesthesia and Intensive Care, Careggi University Hospital, Florence, Italy

Funded by the “ENTE CASSA DI RISPARMIO DI FIRENZE” (protocol number 2013.0331), Firenze/Italy of 25000 Euros. The authors declare no conflict of interest.

Reprints: Alessandro Di Filippo, MD, Department of Health Sciences, Section of Anaesthesia, Intensive Care and Pain Therapy, University of Florence, Careggi University Hospital, Largo Brambilla 3, 50124 Firenze, Italy (e-mail: adifilippo@unifi.it).

Received February 18, 2017

Received in revised form March 29, 2017

Accepted May 31, 2017

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