Pain burden, sensory profile and inflammatory cytokines of dogs with naturally-occurring neuropathic pain treated with gabapentin alone or with meloxicam

Abstract

Canine neuropathic pain (NeuP) has been poorly investigated. This study aimed to evaluate the pain burden, sensory profile and inflammatory cytokines in dogs with naturally-occurring NeuP. Twenty-nine client-owned dogs with NeuP were included in a prospective, partially masked, randomized crossover clinical trial, and treated with gabapentin/placebo/gabapentin-meloxicam or gabapentin-meloxicam/placebo/gabapentin (each treatment block of 7 days; total 21 days). Pain scores, mechanical (MNT) and electrical (ENT) nociceptive thresholds and descending noxious inhibitory controls (DNIC) were assessed at baseline, days 7, 14, and 21. DNIC was evaluated using {Delta}MNT (after-before conditioning stimulus). Positive or negative {Delta}MNT corresponded to inhibitory or facilitatory pain profiles, respectively. Data from baseline were compared to those of sixteen healthy controls. {Delta}MNT, but not MNT and ENT, was significantly larger in controls (2.3 {+/-} 0.9 N) than in NeuP (-0.2 {+/-} 0.7 N). The percentage of dogs with facilitatory sensory profile was similar at baseline and after placebo (61.5-63%), and between controls and after gabapentin (33.3-34.6%). Pain scores were lower than baseline after gabapentin or gabapentin-meloxicam. Cytokine levels were not different between groups or treatments. Dogs with NeuP have deficient inhibitory pain mechanisms. Pain burden was reduced after gabapentin and gabapentin-meloxicam depending on the pain scoring instrument used.