ABSTRACT
BACKGROUND: Anecdotal reports suggest that cannabis users require increased postoperative analgesia but there is insufficient supporting data. METHODS: A prospective randomized study was carried out in 73 patients undergoing elective operations. Postoperatively, all patients were assessed by a blinded investigator, who recorded pain intensity, sedation levels, mood, and hourly analgesia requirements. We calculated the mean pain intensity difference at the first postoperative hour (MPID1) and the sum of pain intensity differences (SPID1). The following end points were compared between cannabis users and non-users using SPSS 16: MPIDI; SPID; patient mood; supplemental analgesia requirements and global assessment scores. RESULTS: There were 42 cannabis users and 31 non-users. Cannabis users had significantly higher supplemental pethidine requirements (82.7 mg, SD = 3.4 vs. 51.6 mg, SD = 42.7, p = 0.003) and significantly greater MPID1 scores (1.88, SD = 1.09 vs. 1.35, SD = 1.12, p = 0.001) compared to non-users. Female cannabis users required significantly more analgesia than males (93.3 mg, SD = 45.8 vs. 78.3 mg, SD = 44.3, p = 0.025). CONCLUSION: Cannabis users require significantly more opioid rescue analgesia in the immediate postoperative period. Further research is needed to elucidate the precise mechanism by which this occurs.