A Single-center, Randomized, Clinical Trial of Opioid-free Analgesia Versus Routine Opioid-Based Analgesia Regimen for the Management of Acute Postoperative Pain Following Cesarean Section

Objective: To determine if opioid-free analgesia is as effective and safe as opioid-based analgesia for post-cesarean section pain. Material and Methods: Non-inferiority, assessor-blinded randomized controlled trial. One hundred cesarean section patients were randomized into 2 arms. Opioid-free analgesia arm had 1 gram intravenous paracetamol infusion and bolus 4 grams intravenous 20% magnesium sulfate preoperatively, then 1 gram/hour infusion of 20% magnesium sulfate intraoperatively until 2 hours post-operation. Postoperatively, they had 100 milligrams of rectal diclofenac 12-hourly and continued paracetamol 6-hourly for 24 hours. Opioid-based analgesia arm had 100 milligrams of rectal diclofenac 12-hourly, 30 milligrams of intramuscular pentazocine 6-hourly, and 1 gram of intravenous paracetamol 6-hourly, postoperatively for 24 hours. Both arms were allowed rescue analgesia with intramuscular pentazocine. Primary outcomes were pain intensity at 4, 8, and 24 hours post-operation and postoperative pentazocine use. Non-inferiority limit was a mean difference in pain score <1.3. Results: Postoperative pain scores at 4, 8, and 24 hours were lower in the opioid-free analgesia arm; mean difference -0.18; 95% confidence interval (CI): -0.70-0.34; p=0.499, -0.10; 95% CI: -0.78-0.59; p=0.782 and -0.31; 95% CI: -0.89-0.29; p=0.308 respectively. Mean pentazocine use was lower in the opioid-free analgesia arm (52.83±21.85 mg/164.40±28.59 mg; p=0.001). Serious adverse event occurred in one (2.0%) participant in the opioid-free analgesia arm and none in the opioid-based analgesia arm, p=0.315. There was no significant difference in the 5th-minute Apgar score (p=0.315). Conclusion: Opioid-free analgesia using perioperative intravenous magnesium sulfate, intravenous paracetamol, and postoperative rectal diclofenac is non-inferior to and as safe as the opioid-based analgesia and it reduced pentazocine consumption.