Gabapentin for Pain Management after Major Surgery: A Placebo-controlled, Double-blinded, Randomized Clinical Trial (the GAP Study)

Background:
Gabapentin is an anticonvulsant medication with approval for use in neuropathic pain and epileptic disorders. It is frequently added to multimodal analgesic regimens during and after surgery to reduce opioid use while controlling pain effectively. There is little evidence to show its effectiveness in major surgery.

Methods:
In this multicenter, double-blinded randomized controlled trial, adults undergoing major cardiac, thoracic, or abdominal surgery were randomized to receive either gabapentin (600 mg before surgery, 300 mg twice daily for 2 days after surgery) or placebo. The primary outcome was length of hospital stay. Secondary outcomes included acute and chronic pain, total opioid use, adverse health events, and health-related quality of life. Patients were followed up daily in-hospital until discharge and then at 4 weeks and 4 months after surgery.

Results:
A total of 1,196 participants were randomized (500 underwent cardiac, 346 thoracic, and 350 abdominal surgery); 596 were allocated to placebo, and 600 were allocated to gabapentin. Median length of hospital stay was similar in the two groups (gabapentin, 5.94 [interquartile range (IQR), 4.08 to 8.04] days; placebo, 6.15 [IQR, 4.22 to 8.97] days; hazard ratio, 1.07; 95% CI, 0.95 to 1.20; P = 0.26). Overall, 384 participants experienced one or more serious adverse events (gabapentin, 189 of 596 [31.7%]; placebo, 195 of 599 [32.6%]), with some variation across surgical specialties.

Conclusions:
Among patients undergoing major cardiac, thoracic, and abdominal surgery, adding gabapentin to multimodal analgesic regimes did not alter the length of hospital stay or the number of serious adverse events.