Determination of sensitivity to metocurine in exercised horses.

The research study examined the possible effect of consistent exercise on the sensitivity to the muscle relaxant metocurine in horses. It was found that despite conditioning, there was no significant change in the sensitivity of their neuromuscular junction to the drug.

Exercise Protocol and Verification

• The study involved five Thoroughbreds undergoing an exercise regime involving treadmill sessions thrice a week for a duration of 8 months. The protocol was designed based on previous studies done on dogs.
• The physiological response to the exercise regime was measured using the maximal rate of O2 consumption, which showed that the horses had reacted to the exercise conditioning.

Control Group

• In parallel to the monitored exercise regime, six non-exercised Thoroughbreds were maintained as a control group to compare their sensitivity to metocurine.

Drug Administration and Monitoring

• The effect of metocurine was studied under certain conditions. The horses were under general anesthesia and were partially paralyzed using a brief constant-rate infusion of the metocurine iodide.
• The degree of paralysis was measured using the hoof twitch response, along with simultaneous quantification of blood metocurine. This was used to evaluate the sensitivity of the neuromuscular junction to metocurine.

Analysis and Results

• The generated data on pharmacokinetics and pharmacodynamics were analyzed using a nonlinear regression program based on the Hill equation.
• The results revealed no significant differences between exercised and non-exercised horses in their sensitivity to the muscle relaxant metocurine.
• The mean blood concentration required for a 50% paralyzing dose of metocurine was 0.44 +/- 0.11 (SD) microgram/ml in exercised horses, and 0.58 +/- 0.22 microgram/ml in non-exercised horses, indicating a marginal variance.

Conclusion

• The study concluded that even though the horses responded to the exercise conditioning, it did not result in a significant change in the sensitivity of the neuromuscular junction to metocurine. This indicates that exercise conditioning does not affect the dosing requirement of the muscle relaxant in horses.