Effects of cocaine on incremental treadmill exercise in horses.

This study explores the effects of cocaine on horses during an incremental treadmill test. Two different doses of the drug were administered to four mature horses, and their hemodynamics and various performance measurements were recorded and analyzed.

Introduction and Methods

• The research aimed to determine the effects of cocaine, an illicit stimulant drug, on the performance and physiological responses of four mature horses during an incremental treadmill exercise.
• In the study, two different doses (50 mg and 200 mg) of cocaine were intravenously injected into each horse.
• The study measured various parameters including the maximal heart rate (HRmax), treadmill velocity at HRmax, treadmill velocity needed to produce a blood lactate concentration of 4 mmol/l, maximal mixed venous blood lactate concentration, maximal treadmill work intensity, and the overall duration of the incremental treadmill test.

Results

• Both doses of cocaine were found to increase the maximal heart rate (HRmax) by approximately 7%.
• In the exercise test, during the 4- to 7-m/s steps, mean arterial pressure rose to 30 mmHg in the 200-mg cocaine trial, a significant increase compared to non-cocaine trials.
• Neither dose of cocaine had any effect on right atrial pressure, right ventricular pressure or maximal change in right ventricular pressure over time.
• However, the administration of cocaine significantly increased the maximal mixed venous blood lactate concentration. The increase was 41% with the 50-mg dose and 75% with the 200-mg dose during exercise.
• The treadmill velocity needed to produce a blood lactate concentration of 4 mmol/l was decreased from approximately 6.9 and 6.8 m/s in non-cocaine trials to 4.4 m/s in the 200-mg cocaine trial.
• The maximal treadmill work intensity was not altered by cocaine administration.
• However, during the 200-mg trial, the time to exhaustion increased by approximately 92 seconds, or 15%, indicating that cocaine administration may influence endurance.

Conclusion

• This study provides compelling evidence that cocaine use can significantly affect a horse’s cardiovascular response to exercise and its endurance levels.
• The increased heart rate and blood lactate levels suggest that cocaine causes elevated stress on the horse’s cardiovascular system during exercise.
• Further research is recommended to explore the wider implications of these effects and the potential consequences for equine health and performance.