The efficacy of dantrolene sodium in controlling exertional rhabdomyolysis in the Thoroughbred racehorse.

The research article explores how dantrolene sodium can effectively manage exercise-induced rhabdomyolysis in Thoroughbred racehorses, evident from a decrease in the horses’ serum creatine kinase levels post-exercise upon administering the drug.

Objective of the Study

• The main goal of this research was to assess the potential of dantrolene sodium, a muscle relaxant, in controlling exercise-induced rhabdomyolysis (ER) in Thoroughbred racehorses, despite the lacking supporting data. ER, a condition usually caused by muscle damage, is commonly seen in racehorses due to their high levels of physical activity.

Methods

• The study was carried out through a double-blind, randomized, placebo-controlled crossover trial involving 77 Thoroughbred racehorses in Newmarket, UK.
• The horses were each given either 800 mg dantrolene sodium or a color-matched placebo orally one hour prior to exercise. The treatments were switched between the experimental groups after a week – a design known as “crossover” – making every horse its own control.
• The researchers evaluated the ER degrees in horses using measured serum creatine kinase (CK) levels. CK is an enzyme released into the blood when there is muscle damage. The CK levels were measured before the exercise and again six hours after it. The change in level was used to calculate the difference for each horse between the two treatment periods.

Results

• The average difference in CK levels for all horses was +104.8 iu/l. Statistically speaking, the results indicated a significant difference in CK values between placebo and dantrolene treatments, rejecting the null hypothesis – suggesting the drug had an effect.
• Moreover, no horses subjected to dantrolene showed ER signs after exercise, while three horses receiving the placebo exhibited symptoms of the condition. The incidence of ER in the placebo group accounted for around 4% of the horses involved (3/77).

Conclusions

• From the results, it is inferred that dantrolene sodium’s oral administration had a significant effect on reducing the difference in plasma CK levels before and after exercise. This finding was in comparison to the placebo treatment and suggested the prevention of ER in susceptible subjects.
• The findings propose that dantrolene sodium could be helpful in managing ER in Thoroughbred racehorses. However, the researchers suggest further inquiries should be made into horses’ pre- and post-exercise calcium levels and the repeatability of the study late in the season with increased energy rationing and more intense exercise.