Efficacy of Intravenous Dexamethasone Versus Placebo in Experimental Foot Lameness in Horses

Abstract

IntroductionThere are no refereed blinded controlled documentations of the skeletal analgesic efficacy of intravenous dexamethasone. The objective was to test the hypothesis that intravenous dexamethasone is more efficacious in alleviating lameness than placebo in a reversible adjustable heart bar shoe model of equine foot pain.MethodsEight healthy horses (7 Thoroughbreds, 1 Warmblood, aged 6.5 ± 3.3 years, age range 2–11 years) underwent weekly intravenous treatments 1 hour after lameness induction. Treatments were isotonic saline placebo at 1 ml/45 kg bwt, or dexamethasone (2 mg/ml in polyethylene glycol) at 0.045 mg/kg bwt, a typical dose used twice daily in the USA for anti‐inflammatory effect. Treatments were randomly assigned and administered by a co‐investigator who had no input on Heart Rate (HR) and Lameness Score (LS) measurements. Another investigator unaware of treatment assignments monitored HR and LS every 20 min for 5 hours after lameness induction and then hourly through 12 hours post‐treatment. One week later treatment assignments were reversed and the experiment was repeated. Repeated measures ANOVA and post hoc Tukey's test were used to identify significant effects at P<0.05.ResultsAfter treatment, mean HR and LS were not different between treatments (P>0.05). HR and LS remained elevated over pre‐lameness values throughout the 13‐hour post‐lameness monitoring period (P<0.05).ConclusionsIt was concluded that intravenous dexamethasone was no more effective than saline placebo. Neither treatment was effective at alleviating lameness over a 12‐hour post‐treatment period in this model. Dexamethasone at 0.045 mg/kg bwt should not affect acute foot lameness during equine exercise or performance.Ethical Animal ResearchThe study was approved by the University of Illinois Institutional Animal Care and Use Committee. Sources of funding: Fédération Equestre Internationale. Competing interests: none.