Hot Literature: What's the scoop on gabapentin?

Pain management in veterinary medicine is getting a lot of attention these days. One medication, gabapentin, an anticonvulsant shown to reduce neuropathic pain and acute postsurgical pain in human medicine, is attracting interest from veterinary researchers. A recent study looked at the effects of gabapentin for use as adjunctive perioperative pain control in dogs.

Thirty client-owned dogs scheduled for forelimb amputation because of a diagnosis of cancer, but free of other underlying illness, were randomly divided into two groups. One group received gabapentin (10 mg/kg) orally once before surgery and then a 5-mg/kg dose every 12 hours for three days. The other group received a placebo. The veterinary technical staff and owners were unaware of whether patients were receiving gabapentin or placebo. For all of the dogs, preanesthetic medications included glycopyrrolate and methadone. Anesthesia was induced with intravenous fentanyl, midazolam, and propofol and maintained with isoflurane, which was supplemented with a continuous-rate infusion of fentanyl throughout the surgical procedure. Local anesthetic infiltrating the brachial plexus before amputation was also implemented. After surgery, the intravenous fentanyl was increased or decreased based on patient comfort and behavior. Additional analgesics or sedatives were also allowed.

Each patient's pain level was evaluated before surgery and at two-hour intervals for 18 hours after tracheal extubation. Separate pain evaluations were performed at 18-hour intervals while the patients were still in the hospital using various pain evaluation methods including the Glasgow Composite Pain Scale short form and the University of Melbourne Pain Scale. Owners were then asked to report on their dogs' activity, appetite, and wound soreness for three days after discharge.

While there was a wide range in the initial individual presurgical pain scores, the results of this study did not find a significant difference in pain evaluations between the two groups, either in the hospital or at home. The use of constant-rate infusion fentanyl was similar in both groups, and the use of other analgesics did not differ significantly.

Despite the frequent recommendation for using gabapentin to manage chronic pain in dogs, there is little data available evaluating its efficacy. This study did not find a short-term benefit of gabapentin on postsurgical pain. However, that does not necessarily suggest that it has no effect. The sample size for this study was small, and the baseline pain scores were significantly different in these cancer patients. Additionally, dogs in this study received several other analgesics, and the administered gabapentin was at the low end of the recommended dose range. Higher doses administered more frequently may have produced different results. Further research analyzing different doses and dosing frequencies as well as examining the use of gabapentin for other painful disease conditions is needed before the efficacy and possible analgesic benefits can be determined.

Wagner AE, Mich PM, Uhrig SR, et al. Clinical evaluation of perioperative administration of gabapentin as an adjunct for postoperative analgesia in dogs undergoing amputation of a forelimb. J Am Vet Med Assoc 2010;236(7):751-756.

Abstract available at http://avmajournals.avma.org/doi/abs/10.2460/javma.236.7.751