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OBSTETRIC ANESTHESIOLOGY

A Randomized Controlled Trial of Pentazocine Versus Ondansetron for the Treatment of Intrathecal Morphine-Induced Pruritus in Patients Undergoing Cesarean Delivery

Decha Tamdee, MSc^*, Somrat Charuluxananan, MD, MSc, FRCAT, Yodying Punjasawadwong, MD, M.Med.Sc., FRCAT, Chamaiporn Tawichasri, MSc^*, Jayanton Patumanond, MD, MPH, DSc^*, and Pin Sriprajittichai, MD, MSc, FRCAT

From the *Ph.D. Program in Clinical Epidemiology, Faculty of Medicine, Chiang Mai University, Chiang Mai; Department of Anesthesiology, Faculty of Medicine, Chulalongkorn University, Bangkok; and Department of Anesthesiology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.

Address correspondence and reprint requests to Somrat Charuluxananan, MD, MSc, FRCAT, Department of Anesthesiology, Faculty of Medicine, Chulalongkorn University, Rama IV Rd., Patumwan, Bangkok 10330, Thailand. Address e-mail to somratcu{at}hotmail.com.

Abstract

BACKGROUND: Ondansetron is effective for the treatment of intrathecal morphine-induced pruritus. There is evidence that -opioid receptor agonists have antipruritic activity. Pentazocine is an agonist of -opioid receptors and partial agonist at µ-opioid receptors. We therefore performed a randomized, double-blind trial to compare the efficacy of pentazocine and ondansetron for the treatment of pruritus associated with intrathecal injection of morphine in patients undergoing cesarean delivery.

METHODS: Two hundred eight parturients who developed moderate to severe pruritus after the administration of intrathecal morphine were randomly allocated to 2 groups: IV pentazocine 15 mg (n = 104) and IV ondansetron 4 mg (n = 104). The successful treatment of pruritus (no or mild pruritus) and other adverse effects were determined 15 min after study drug administration, and patients were observed for recurrence of pruritus for 4 h.

RESULTS: The treatment success rate at 15 min was higher in the pentazocine group (96.1%) than in the ondansetron group (80.8%) (95% confidence interval of difference: 7.0%, 23.8%; P = 0.001). The recurrence rate of moderate to severe pruritus within 4 h after treatment in the pentazocine group (12.0%) was lower than in the ondansetron group (32.1%) (P = 0.001). There were no significant differences between groups in nausea/vomiting, sedation, shivering, pain scores, and pain at injection site. No respiratory depression was observed.

CONCLUSIONS: Pentazocine 15 mg is superior to ondansetron 4 mg for the treatment of intrathecal morphine-induced pruritus and has a lower recurrence rate. The side effects after treatment are mild.