The effect of the organophosphate trichlorfon on the neuromuscular blocking activity of atracurium in halothane-anesthetized horses.

This study investigates the possible interaction between the organophosphate trichlorfon and neuromuscular blocking drug atracurium in halothane-anesthetized horses. It is concluded that trichlorfon doesn’t significantly influence the neuromuscular blocking activity of atracurium even when it reduces the activity of cholinesterase enzyme in blood.

Study Design and Methodology

• The research was conducted on six horses which were anesthetized and paralyzed using the drug atracurium on the first day of the experiment. A total of five injections of atracurium per horse were administered.
• After six days, the horses were given the organophosphate trichlorfon, which is a cholinesterase inhibitor.
• On the seventh day, the same procedure with atracurium was repeated.
• Tests were conducted to measure the level of activity of the enzyme cholinesterase in the horse’s blood on the first and seventh days before the anesthesia.
• To measure the effect of atracurium, the time taken from the injection to the maximum reduction in hoof twitch was noted. The time taken for recovery from maximum twitch reduction to 10% and from 10 to 75% was also recorded.
• Finally, the antagonist drug edrophonium was administered to observe its effect on the muscle twitch height and on the cardiovascular parameters like arterial blood pressure and heart rate.

Findings of the Study

• Despite the reduction of the cholinesterase activity by trichlorfon to just 16% of its original value, no significant difference was observed in the neuromuscular blocking activity of atracurium between the two experimental days.
• The onset of the atracurium action was slower for the first injection compared to subsequent ones. However, the time taken for recovery was found to be the same for all injections and did not differ between the two experimental days.
• Administration of the antagonist drug edrophonium resulted in the quick recovery of the muscle strength to its pre-atracurium state while causing a significant increase in the arterial blood pressure. The change in heart rate was variable.

Conclusions

• The study concludes that the cholinesterase inhibitor trichlorfon does not significantly affect the neuromuscular blocking activity of atracurium.
• The findings indicate that atracurium can be used in anesthesia without significant interaction with trichlorfon. More studies may be required to further validate this finding in other species and in different clinical settings.