The efficacy of dantrolene sodium in controlling exertional rhabdomyolysis in the Thoroughbred racehorse.
Authors: Edwards J G T, Newtont J R, Ramzan P H L, Pilsworth R C, Shepherd M C
Journal: Equine veterinary journal
Summary
# Editorial Summary: Dantrolene Sodium for Exertional Rhabdomyolysis in Racehorses Exertional rhabdomyolysis (ER) remains a significant problem in Thoroughbred racing, yet clinical treatments have relied largely on anecdotal evidence rather than rigorous investigation. Edwards and colleagues conducted a randomised, double-blind, placebo-controlled crossover trial with 77 Newmarket racehorses to evaluate whether oral dantrolene sodium (800 mg administered 1 hour before exercise) could reduce the muscular damage characteristic of ER. Using serum creatine kinase (CK) as their primary measure—calculating the difference between post-exercise and baseline levels—the researchers found that dantrolene treatment produced a mean reduction of 104.8 iu/l compared with placebo (P = 0.0013), and notably, none of the horses receiving dantrolene developed clinical ER signs, whereas three placebo-treated horses did. For practitioners managing susceptible individuals or those returning to work after box rest, these findings suggest dantrolene offers a practical pharmacological option; however, the relatively low overall ER incidence (4%) and the authors' recommendation for further investigation during high-intensity training periods and elevated energy feeding warrant cautious interpretation of efficacy in different competitive contexts.
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Practical Takeaways
- •Dantrolene sodium appears effective for preventing exercise-induced rhabdomyolysis in susceptible racehorses; consider using 800 mg orally 1 hour before return-to-work exercises after rest periods
- •Horses with a history of ER episodes may particularly benefit from dantrolene prophylaxis, as the drug prevented all clinical episodes in this study population
- •Further research into optimal dosing, timing, and efficacy during high-intensity racing seasons with elevated energy rations is warranted before widespread adoption
Key Findings
- •Oral dantrolene sodium 800 mg administered 1 hour before exercise significantly reduced post-exercise serum creatine kinase (CK) rise compared to placebo (mean difference +104.8 iu/l, P = 0.0013)
- •No horses receiving dantrolene sodium developed clinical signs of exercise-induced rhabdomyolysis, whereas 3 horses (3.9%) in the placebo group developed clinical ER
- •The randomised, double-blind, placebo-controlled crossover design with each horse acting as its own control strengthened the evidence for dantrolene efficacy in Thoroughbred racehorses