Prophylactic Pentazocine Reduces the Incidence of Pruritus After Cesarean Delivery Under Spinal Anesthesia With Opioids: A Prospective Randomized Clinical Trial

BACKGROUND: The incidence of pruritus after cesarean delivery under spinal anesthesia with opioids is high, ranging from 50% to 100%. Pruritus is difficult to prevent; however, pentazocine has been shown to be an effective treatment. Despite this, the prophylactic effect of pentazocine on pruritus has not been defined. This randomized double-blind trial aimed to evaluate the effect of intraoperative IV pentazocine on the incidence of opioid-induced pruritus within the first 24 hours after administration of neuraxial opioids. METHODS: We obtained institutional review board approval and written informed consent from the 122 patients (American Society of Anesthesiologists [ASA] physical status II; aged 20–40 years) scheduled for elective cesarean delivery who were included in this study. Spinal anesthesia was performed with 10 mg of 0.5% hyperbaric bupivacaine, 10 &mgr;g of fentanyl, and 100 &mgr;g of morphine. After delivery of the baby and placenta, the parturient women were randomized to intravenously receive 15 mg (1 mL) of pentazocine or 1 mL of saline. All women received postoperative analgesia with the epidural infusion of 0.15% levobupivacaine. The presence of pruritus within the first 24 hours after intrathecal administration of opioids was recorded, and severity of itch, numerical rating scale (NRS) for pain, and adverse effects were also recorded at the time of the arrival on the ward, as well as 3, 6, 12, and 24 hours after the intrathecal administration of opioids. RESULTS: A total of 119 women completed the study. IV pentazocine reduced the overall incidence of pruritus within the first 24 hours compared to IV saline, with an estimated relative risk of 69% (95% confidence interval [CI], 52%, 90%; P = .007). IV pentazocine also reduced the severity of pruritus. The incidence of nausea and vomiting was not significantly different. There were no significant differences in postoperative NRS scores. CONCLUSIONS: A single 15-mg dose of IV pentazocine after delivery can reduce both the incidence and severity of pruritus in women who have received subarachnoid opioids during cesarean delivery.