Tapentadol vs oxycodone for postoperative pain treatment the first 7 days after total knee arthroplasty: a randomized clinical trial

Pain after total knee arthroplasty is a prevalent condition. This study compared the effectiveness of tapentadol extended-release (ER) 50 mg x 2, oxycodone controlled-release (CR) 10 mg x 2, and placebo, as added to a multimodal analgesic regime both in-hospital and at home the first week after total knee arthroplasty. The study was randomized and blinded for investigators, staff, outcome assessors, and patients. Follow-up included pain intensity on mobilization, pain at rest, worst pain in the previous 24 hours, and adverse effects measured on 0 to 10 numerical rating scales. A total of 134 patients in 3 study groups received their allocated intervention and were included in the analysis. The primary outcome pain on mobilization the 7 first postoperative days reported as area under the curve was 528.1 (SD 267.5, interquartile range (IQR) 356.6-665.4) for placebo, 427.2 (SD 203.9, IQR 303.6-544.3) for tapentadol ER, and 507.9 (SD 243.7, IQR 292.4-686.8) for oxycodone CR (P = 0.12). With the exception of constipation being less prevalent in the tapentadol ER group (P = 0.02), we found no significant differences between treatment groups for the secondary outcomes. Tapentadol ER as an add-on to multimodal analgesia did not significantly improve pain relief when compared to oxycodone CR or placebo. Constipation was lowest in the tapentadol ER group.