Abstract: We included five RCTs with a total of 227 participants (age range 23 to 76 years; 65% men) with acute pancreatitis pain. The opioids assessed were intravenous and intramuscular buprenorphine, intramuscular pethidine, intravenous pentazocine, transdermal fentanyl and subcutaneous morphine. One RCT, comparing subcutaneous morphine with intravenous metamizole reported non-significant reduction in the number of participants with improvements in pain intensity (primary outcome) (RR 0.50, 95% CI 0.19 to 1.33). Three studies compared analgesia using opioids with non-opioid treatments. After excluding one study that used opioids through continuous intravenous infusion, there was a decrease in the number of patients requiring supplementary analgesia (RR 0.53, 95% CI 0.30 to 0.93). In a single study, there were no differences in the number of patients requiring supplementary analgesia between buprenorphine and pethidine (RR 0.82, 95% CI 0.61 to 1.10). Pancreatitis complications were not associated with a significant difference between the drugs tested. No clinically serious or life-threatening adverse events occurred related to treatment. No differences for this outcome were found between opioid and non-opioid treatments, or for type of adverse event (nausea-vomiting and somnolence-sedation). One death in the procaine group was reported across all the trials. One RCT comparing pethidine with intramuscular buprenorphine reported non-significant differences of supplementary analgesic, adverse events or deaths. One RCT comparing fentanyl with placebo found no difference in adverse events. The findings of this review are limited by the lack of information to allow full appraisal of the risk of bias, the measurement of relevant outcomes and the small numbers of participants and events covered by the trials. Opioids may be an appropriate choice in the treatment of acute pancreatitis pain. Compared with other analgesic options, opioids may decrease the need for supplementary analgesia. There is currently no difference in the risk of pancreatitis complications or clinically serious adverse events between opioids and other analgesia options. Future research should focus on the design of trials with larger samples and the measurement of relevant outcomes for decision-making, such as the number of participants showing reductions in pain intensity. The reporting of these RCTs should also be improved to allow users of the medical literature to appraise their results accurately. Large longitudinal studies are also needed to establish the risk of pancreatitis complications and adverse events related to drugs.

Plain-language summary: For participants needing additional pain relief, combined analysis of opioids (pentazocine and morphine) showed a significant benefit when compared with non-opioid treatments. Two trials showed that buprenorphine and pentazocine were each more effective than procaine. Our confidence in the stability of these effects is low, however, due to limitations in the number of studies and participants, and the low quality of the way the trials were run and reported. No serious or life-threatening adverse events were linked to the drugs being studied. One death was reported, in a procaine group, across all the included trials. On the evidence so far, opioids may be an appropriate treatment option and might have the advantage of decreasing the need for additional pain relief. We found no clear difference in the risk of pancreatitis complications or serious adverse event between opioids and other pain relief treatments. However, the findings of this review are limited by the lack of information to allow full appraisal of the risk of bias, the measurement of relevant outcomes and the small numbers of participants covered by the trials.