Gabapentin does not improve multimodal analgesia outcomes for total knee arthroplasty: a randomized controlled trial

This study assessed whether gabapentin given preoperatively and for two days postoperatively (in addition to patient-controlled analgesia [PCA] morphine, acetaminophen, and ketorolac) is effective in reducing morphine requirements and moderating pain scores when compared with placebo for primary total knee arthroplasty. This single-centre double-blind randomized controlled trial was undertaken in patients who underwent primary total knee arthroplasty. All subjects received acetaminophen 1,000 mg and ketorolac 15 mg po preoperatively. Postoperatively, subjects received PCA morphine, acetaminophen 1,000 mg every six hours, and ketorolac 15 mg po every six hours. Subjects received either gabapentin 600 mg po preoperatively followed by 200 mg po every eight hours for two days or matching placebo. The primary outcome was cumulative morphine consumption at 72 hr following surgery. Secondary outcome measures included pain scores and patient satisfaction. There were 52 subjects in the gabapentin group and 49 subjects in the placebo group. The average cumulative morphine consumption at 72 hr postoperatively was 66.3 mg in the gabapentin group and 72.5 mg in the placebo group (difference -6.2 mg; 95% confidence interval -29.1 to 16.8 mg; P = 0.59). Mean pain scores at rest, with passive movement, or with weight bearing were similar in both groups at corresponding time periods for the first three days following surgery. In addition, mean patient satisfaction scores and hospital length of stay were similar in the two groups. Gabapentin 600 mg po given preoperatively followed by 200 mg po every eight hours for two days has no effect on postoperative morphine consumption, pain scores, patient satisfaction, or length of hospital stay. This trial is registered at ClinicalTrials.gov NCT01307202.