Eighty-two RCTs were included in the review. On the Jadad quality scale 10 trials scored 2, 14 trials scored 3, 22 trials scored 4 and 36 trials scored 5.
NSAIDs (25 trials): Approximately half of the studies showed benefits in either pain scores or rescue analgesic consumption using NSAIDs. Among them, parecoxib and combination of paracetamol and ketoprofen were most effective in decreasing pain as well as decreasing morphine consumption.
NMDA receptor antagonists (eight trials): Trials using ketamine showed analgesic effects and decreased opioid consumption. A single study of dextromethorphan did not show any benefits whereas methadone showed benefits without causing additional adverse effects.
Gabapentinoids (six trials): Pain control was improved with gabapentin at early time point (two hours or postanaesthesia care unit discharge) but not at later time points. It was also effective in decreasing 24 hours cumulative opioid consumption.
Epidural or intrathecal analgesia (43 trials): Single-dose epidural analgesia using opioids, local anaesthetics or their combination was found to be ineffective in improving postoperative pain control. However, a combination of these with clonidine or steroid decreased pain as well as morphine consumption. Continuous epidural analgesia with opioids and local anaesthetics did not provide a significant effect but using either opioids or local anaesthetics showed benefit. Use of intrathecal analgesia reduced pain in the immediate postoperative period but no benefit was observed in extended period.