Does postoperative low-dose duloxetine provide analgesic effect and lower morphine consumption after primary total knee arthroplasty? A prospective, double-blind, randomized controlled trial.

Abstract

Introduction: Duloxetine as an adjunct analgesic has shown effective results in trials of patients undergoing total knee arthroplasty (TKA). However, the regimen has not been standardized. We, therefore, evaluated the analgesic efficacy of low-dose duloxetine after TKA.

Materials and methods: We conducted a double-blind, randomized controlled trial of patients undergoing unilateral primary TKA, comparing 30 mg/d of duloxetine for 6 weeks as an additive medication for pain control to modern multimodal analgesia after TKA. The primary outcome measure was a visual analogue scale (VAS) for pain at rest, during walking, and at night at 24 h, 72 h, 2 weeks, 6 weeks, and 12 weeks after the operation. Secondary outcomes were morphine consumption, adverse events, and functional outcomes: Oxford Knee Score, Knee injury and Osteoarthritis Outcome Score (KOOS).

Results: Mean VAS for pain at rest, during walking, and at night at 24 h, 72 h, 2 weeks, 6 weeks, and 12 weeks showed no significant differences between the two groups, except a significantly lower mean VAS at night at 2 weeks in the duloxetine group. Mean total morphine consumption (0-72 h) was 33% less in the duloxetine group (6.8 ± 5.7 vs. 10.2 ± 7.3 mg, p = 0.04). There were no significant differences in adverse events and functional outcomes except better KOOS symptoms at 6 and 12 weeks in the duloxetine group.

Conclusion: Low-dose duloxetine could reduce postoperative morphine consumption and improve KOOS symptoms at 6 and 12 weeks with good tolerability. However, it did not significantly reduce pain at rest or during walking. Low-dose duloxetine can be considered an addition to contemporary multimodal pain management after TKA.

Level of evidence v: Therapeutic Level I.