Assessment of the effects of adjunctive gabapentin on postoperative pain after intervertebral disc surgery in dogs

Abstract

Objective: To assess the effect of adjunctive gabapentin (GBP) on pain after thoracolumbar intervertebral disc surgery in dogs.

Study design: Prospective, randomized, controlled, clinical, 'blinded' trial.

Animals: Sixty-three client owned dogs undergoing hemilaminectomy

Methods: Dogs were assigned to two treatment groups. The GBP group received gabapentin 10 mg kg(-1) orally every 12 hours starting before anaesthesia; the placebo (P) group received empty gelatin capsules. Background analgesia was initiated with intravenous levomethadone 0.6 mg kg(-1) (as the combination 'L-Polamivet) at anaesthesia induction, followed by a fentanyl patch and levomethadone 0.2 mg kg(-1) subcutaneously every 8 hours for 24 hours. Pain was assessed by the short form of the Glasgow Composite Measure Pain Score (CMPS-SF) without the gait category, and by a Visual Analogue Scale (VAS). Serum GBP concentrations and cortisol concentrations were measured. Statistical analyses utilized chi square test, Kolmogorov-Smirnov test, two-way analysis of variances for repeated measurements, Wilcoxon test and Friedmann test as relevant. Correlations were tested by Spearman's and Pearson's correlation coefficient. p < 0.05 was considered significant.

Results: Median CMPS-SF was lower in group GBP than in group P on days 0.5, 1, 4 and 5. However, CMPS-SF and VAS were not significantly different between groups. Both pain scores decreased significantly over time. Cortisol concentrations were not significantly different between groups. Minimum serum concentrations of GBP fell below the detection limit of 1 μg mL(-1) in 6 of 29 and 7 of 28 dogs at 24 and 72 hours, respectively.

Conclusions and clinical relevance: 10 mg kg(-1) GBP orally twice a day did not result in a detectable reduction in pain behaviour compared to background opioid analgesia alone, although a trend to lower pain levels (p < 0.1) was present. Further studies are needed to determine if this is related to effective background analgesia or an ineffective dose of GBP.