Sixteen RCTs (n=1,151) were included in the review.
Gabapentin 1,200 mg single dose pre-operatively.
Gabapentin was associated with a statistically significant decrease in pain intensity at rest compared with placebo at 6 hours (6 RCTs; WMD -16.55 mm, 95% CI: -25.66, -7.44, p=0.0004) and 24 hours (3 RCTs; WMD -10.87 mm, 95% CI: -20.90, -0.84, p=0.03). The χ2 test suggested statistically significant heterogeneity between studies (p<0.00001).
Gabapentin was also associated with a statistically significant decrease in cumulative opioid consumption compared with placebo, (3 RCTs; WMD -27.9 mg, 95%: -31.52, -24.29, p<0.00001) and a statistically significant delay in the time to first request for analgesia (2 RCTs; WMD 7.42 minutes, 95% CI: 0.49, 14.34, p=0.04). Statistically significant heterogeneity was not indicated. Gabapentin was associated with a lower risk of vomiting (6 RCTs; Peto OR 0.42, 95% CI: 0.24, 0.76; NNT 8) and less risk of urinary retention (figures not reported; NNT 7). There was no statistically significant difference in any other adverse effects between gabapentin and placebo.
Gabapentin <1,200 mg single dose pre-operatively.
Gabapentin was associated with a statistically significant decrease in pain intensity at rest compared with placebo at 6 hours (5 RCTs; WMD -22.43 mm, 95% CI: -27.66, -17.19, p<0.00001) and 24 hours (4 RCTs; WMD -13.18, 95% CI: -19.68, -6.68, p<0.0001). There was evidence of statistically significant heterogeneity at 24 hours (p<0.00001) and 6 hours (p=0.009), (I2=64.8%). Post-operative opioid consumption reduction was significantly reduced with gabapentin compared with placebo (4 RCTs; WMD -15.98, 95% CI: -23.45, -8.50, p<0.0001). There was evidence of statistically significant heterogeneity (p<0.00001). Sedation risk was statistically significantly higher in the gabapentin group compared with placebo (2 RCTs; Peto OR 6.95, 95% CI: 3.96, 12.20; NNH 4). There was no statistically significant difference in other adverse effects between placebo and gabapentin.
Gabapentin given as multiple doses peri-operatively.
There was no statistically significant difference between placebo and gabapentin in pain intensity (2 RCTs) or time to first request for analgesia (1 RCT). One RCT showed a 24% reduction in 24-hour cumulative opioid consumption in the gabapentin group compared with placebo.
There was a statistically significant lower incidence of nausea (5 RCTs; Peto OR 0.54, 95% CI: 0.31, 0.95; NNT 9) and pruritus (3 RCTs; Peto OR 0.21, 95% CI: 0.05, 0.87; NNT 13) in the gabapentin group compared with placebo. The difference between these two groups was not statistically significantly different for any other adverse effects, except constipation (OR 0.12, 95% CI: 0.02, 0.9).
Further analyses were reported in the paper.