89: The comparative effectiveness of intravenous acetaminophen versus intravenous morphine for pain relief in early labor: a randomized controlled trial

Abstract

89 The comparative effectiveness of intravenous acetaminophen versus intravenous morphine for pain relief in early labor: a randomized controlled trial Nana-Ama E. Ankumah, Marissa Tsao, Maria Hutchinson, Claudia Pedroza, Jaideep Mehta, Sean Blackwell, Jerrie Refuerzo UT Health University of Texas Medical School at Houston, Houston, TX OBJECTIVE: Intravenous (IV) opioids are common analgesics in early labor, but are limited by marginal pain relief and adverse maternal/fetal effects. Our objective was to compare the effectiveness of IV acetaminophen to IV morphine in reducing pain in early labor. STUDY DESIGN: We conducted an open-label, randomized controlled trial (RCT) of women 34 weeks gestation with regular uterine contractions and cervical dilation 2-6 cm. Women received either IV acetaminophen 1000 mg or IV morphine 2 mg. Women with contraindications to either study drug were excluded. Effectiveness of analgesics was assessed by monitoring the patient’s need for rescue analgesia and by obtaining visual analog scales (VAS) prior and at 15 minutes, 1 hour, 2 hours and 4 hours. VAS scores, rescue analgesics, maternal side effects (nausea, emesis, drowsiness, pruritus, headache, insomnia) and fetal heart rate tracing changes (accelerations, decelerations, baseline change, variability) were compared between groups. An intent-to-treat analysis was performed with chi-square, t-test and logistic regression as appropriate. RESULTS: Of 40 women randomized, 18 received IV acetaminophen (2 did not receive study drug) and 20 received IV morphine. Within 2 hours of analgesics, over half the women who received IV acetaminophen required rescue analgesic demonstrating its minimal effect in pain control (acetaminophen: 52.9 % vs morphine: 17.6%, p1⁄4 0.02). Within 4 hours, there were no differences in rate of rescue analgesics, (acetaminophen: 73.3% vs morphine: 56.3%, p1⁄40.16). VAS scores were similar at each time point for both groups, p>0.05 (Fig 1). Maternal/fetal adverse effects were similar between groups. CONCLUSION: Although overall VAS were comparable between groups across each time interval, over half of women receiving IV acetaminophen required rescue analgesic within 2 hours of treatment. Our findings suggest that IV acetaminophen is less effective for initial pain relief in early labor compared to IV morphine.