Pharmacokinetics and pharmacodynamics of repeat dosing of gabapentin in adult horses.
Authors: Gold Jenifer R, Grubb Tamara L, Cox Sherry, Malavasi Lais, Villarino Nicholas L
Journal: Journal of veterinary internal medicine
Summary
# Gabapentin Dosing in Horses: Safety Profile and Pharmacokinetic Accumulation Gabapentin's potential as an analgesic agent in equine practice remains largely underexplored, with current dosing protocols potentially limiting its therapeutic efficacy. Gold and colleagues administered gabapentin orally to six healthy mares at either 40 or 120 mg/kg twice daily for 14 days, monitoring serum biochemistry, clinical signs of ataxia and sedation, and plasma drug concentrations on days 1 and 15. Both dosing regimens proved well-tolerated with no adverse effects or biochemical changes detected; however, peak plasma concentrations increased substantially with repeated dosing (demonstrating median AUC ratios of 1.5–2.9× between final and initial doses), indicating notable drug accumulation at the higher 120 mg/kg dose. The findings support that gabapentin doses up to 120 mg/kg twice daily are safe from a toxicological standpoint, though the clinical significance of this accumulation—whether it translates to improved analgesia or represents a safety concern—requires further investigation in horses with naturally occurring pain conditions. Equine practitioners considering gabapentin for neuropathic or chronic pain management should recognise that traditional dosing may result in increasing plasma levels over time, which could warrant dose adjustment strategies or careful monitoring during extended treatment protocols.
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Practical Takeaways
- •Gabapentin can be safely dosed at 120 mg/kg q12h in horses without causing detectable toxicity or serum chemistry changes over 14 days of treatment
- •Plasma drug accumulation occurs with repeated dosing, particularly at higher doses, which may improve analgesic efficacy but requires further clinical validation
- •High-dose gabapentin protocols appear well-tolerated and warrant investigation as part of multimodal pain management strategies in equine practice
Key Findings
- •Gabapentin at 40 and 120 mg/kg PO q12h for 14 days caused no changes in physiologic or serum biochemistry variables in healthy mares
- •Maximal plasma concentrations were reached within 1 hour, with median peak levels of 7.6 μg/mL (40 mg/kg) and 22 μg/mL (120 mg/kg) on day 15
- •Repeated dosing resulted in accumulation with AUC ratios of 1.5 (40 mg/kg) and 2.92 (120 mg/kg) comparing last to first dose
- •Horses tolerated the high-dose regimens (up to 120 mg/kg) without adverse effects or ataxia/sedation scores changing