The effect of metformin on measurements of insulin sensitivity and beta cell response in 18 horses and ponies with insulin resistance.
Authors: Durham A E, Rendle D I, Newton J E
Journal: Equine veterinary journal
Summary
# Editorial Summary Insulin resistance and associated hyperinsulinaemia are now established as key risk factors for laminitis in horses and ponies, making pharmacological intervention an increasingly attractive strategy for high-risk individuals. Durham and colleagues investigated whether metformin—a first-line agent for insulin resistance in humans—could improve insulin sensitivity and reduce pancreatic beta cell overactivity in equids, treating 18 affected horses and ponies with 15 mg/kg twice daily and using each animal as its own control whilst standardising diet and management. Metformin produced statistically significant improvements in insulin sensitivity and substantially reduced pancreatic beta cell secretion, with the most pronounced effects evident within 6–14 days of treatment initiation, though benefits appeared to plateau or diminish slightly over longer follow-up periods (23–220 days). Whilst clinical improvements in laminitis signs were observed, they were less dramatic than the measurable metabolic changes, suggesting the drug's metabolic effects may take longer to translate to meaningful clinical outcomes or that additional therapeutic measures remain necessary. For practitioners managing metabolically predisposed horses, metformin represents a potentially valuable tool; however, further research is needed to identify which animals are most likely to benefit, optimise dosing protocols, and clarify the drug's pharmacokinetics in equine metabolism.
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Practical Takeaways
- •Metformin may reduce insulin resistance and associated laminitis risk in horses and ponies; consider as part of a multimodal management approach for IR cases
- •Early response to metformin is greater (6-14 days) than longer-term response, so reassessment timing and treatment duration need careful planning
- •While metformin improves metabolic markers, clinical lameness improvement may lag behind biochemical improvement—manage owner expectations accordingly
Key Findings
- •Metformin treatment at 15 mg/kg twice daily significantly improved insulin sensitivity in 18 horses and ponies with insulin resistance
- •Pancreatic beta cell secretion decreased following metformin treatment, with greater effect at 6-14 days post-treatment than at later timepoints (23-220 days)
- •Subjective clinical benefits were observed but were less pronounced than the improvements in insulin resistance parameters
- •Metformin was found to be safe for use in equids