A pilot study of transdermal gabapentin in cats

Abstract Background Clinical use of gabapentin has increased; transdermal delivery in cats is incompletely studied. Objective To evaluate if gabapentin permeates feline skin in vitro and in vivo and to determine if pain scores improve after administration. Animals In vitro: cadaver skin from 6 cats; phase 1: 8 young, healthy client‐owned cats; phase 2: 15 client‐owned geriatric cats. Methods In vitro, gabapentin applied every q12h to ear or cervical skin in diffusion cells. Samples collected at 0, 2, 4, 12, and 24 hours after application. Phase 1: Cats assigned to 1 of 4 groups: 5 mg/kg or 10 mg/kg applied q8h for 5 days to either ear or cervical skin. Serum samples collected predose, and after 1 and 5 days. Phase 2: 10 mg/kg applied q8h for 5 days. Two validated pain scores recorded predose, and after days 1, 5, and 8. Serum samples collected predose, and after days 1 and 5. Samples were frozen at −80°C for concentration analysis utilizing a validated high‐performance liquid chromatography mass‐spectrometry method. Results Gabapentin was identified in all samples. Significant differences in gabapentin concentrations were observed from day 1 to day 5 (P < .02) and in pain scores from predose to day 5 (P < .05) and day 1 to day 5 (P < .05). No differences in pain scores were observed from predose to day 8 (P = .3). Conclusions and Clinical Relevance Gabapentin in a transdermal base penetrates feline skin in vitro, is absorbed systemically in cats, and may help decrease pain scores.