Adding Gabapentin to a multimodal regimen does not reduce acute pain, opioid consumption or chronic pain after total hip arthroplasty

BACKGROUND: Gabapentin (GPN) is effective in reducing post-operative pain and opioid consumption, but its effects with regional anesthesia for total hip arthroplasty (THA) are not known. We designed this study to determine whether (1) gabapentin administration reduces pain and opioid use after THA using a multimodal analgesic regimen including spinal anesthesia; (2) pre-operative administration of gabapentin is more effective than post-operative administration. METHODS: After REB approval and informed consent, 126 patients were enrolled in a double-blinded, randomized-controlled study. Patients received acetaminophen 1 g per os (p.o.), celecoxib 400 mg p.o. and dexamethasone 8 mg intravenously, 1-2 h pre-operatively. Patients were randomly assigned to one of three treatment groups (G1: Placebo/Placebo; G2: GPN/Placebo; G3: Placebo/GPN). Patients received gabapentin 600 mg (G2) or placebo (G1 and G3) 2 h before surgery. All patients had spinal anesthesia [15 mg (3cc) of 0.5% hypobaric bupivacaine with 10 microg of fentanyl]. In the post-anesthetic care unit, patients received gabapentin 600 mg (G3) or placebo (G1 and G2). On the ward, patients received acetaminophen 1000 mg p.o. q6h, celecoxib 200 mg p.o. q12h and a morphine PCA device. Patients were interviewed 6 months post-surgery to determine the incidence and severity of chronic post-surgical pain. RESULTS: Mean+/-SD cumulative morphine (mg) consumption (G1=49.4+/-24.8, G2=47.2+/-30.1 and G3=56.1+/-38.2) at 48 h and pain scores at 12, 24, 36 and 48 h post-surgery were not significantly different among the groups [G1 (n=38), G2 (n=38) and G3 (n=38)]. Side effect profiles were similar across groups. Six months after surgery, the number of patients who reported chronic post-surgical pain (G1=10, G2=12 and G3=9) and the severity of the pain (G1=4.2+/-2.9, G2=4.1+/-2.2 and G3=4.9+/-2.2) did not differ significantly among the groups (P>0.05). CONCLUSIONS: A single 600 mg dose of gabapentin given pre-operatively or post-operatively does not reduce morphine consumption or pain scores in hospital or at 6 months after hip arthroplasty within the context of spinal anesthesia and a robust multimodal analgesia regimen.