The effect of metformin on measurements of insulin sensitivity and β cell response in 18 horses and ponies with insulin resistance


The Liphook Equine Hospital, Forest Mere, Liphook, Hampshire GU30 7JG, UK


Reasons for performing study: Laminitis in equids is a very common debilitating disease, and insulin resistance (IR) and hyperinsulinaemia are increasingly recognised as important predisposing factors. Pharmacological modification of IR and hyperinsulinaemia might reduce the risk of laminitis.

Hypothesis: Metformin, a drug commonly prescribed for treatment of human IR, may also decrease IR in equids.

Methods: Eighteen horses and ponies with IR and recurrent laminitis were treated with 15 mg/kg bwt metformin per os q. 12 h. Each animal served as its own control by comparing pre- and post treatment proxies for IR, insulin sensitivity (IS) and pancreatic β cell function while controlling for possible dietary and managemental influences on IR.

Results: Evidence of significantly improved IS and decreased pancreatic β cell secretion was found following metformin treatment. The magnitude of effect was greater at earlier resampling (6–14 days) than at later times (23–220 days). Apparent subjective clinical benefits were good but less favourable than effects on IR.

Conclusions: Metformin is safe and appears to increase IS in equids.

Potential relevance: Metformin may be indicated as a treatment for IR in equids. Further studies are required to define appropriate selection of subjects warranting therapy, dosing schedule and pharmacokinetics.