Pharmacokinetics and clinical effects of a subanesthetic continuous rate infusion of ketamine in awake horses.

The research article focuses on determining the impact, dosage suitability, and pharmacokinetics of continuous ketamine infusion in horses, without inducing anesthetic effects.

Objective of Research

• The main aim of this research was to study the pharmacokinetics – how the drug is absorbed, distributed, metabolized and eliminated in the body – and the clinical implications of a constant, subanesthetic amount of ketamine given to healthy, awake horses.

Methodology

• Initially, in a pilot study, ketamine hydrochloride was given to two horses at varying dosage rates for six hours to discern an appropriate dose that did not cause any negative effects.
• The research work was later carried out on six horses where the ketamine dosage was administered for twelve hours at different time intervals and varying rates.
• Different physiological parameters like heart rate, respiratory rate, blood pressure along with physical activity were all recorded before, during, and after the ketamine infusion, helping researchers understand the impact of dosage.
• An additional analgesic test was conducted by applying a modified hoof tester with calculated force on the withers and radius of the horse.

Results

• The results revealed that the ketamine infusion, whether at 0.4 or 0.8 mg/kg/h dosage, produced no signs of behavioral changes or excitement in the horses. Also, there were no significant shifts in the measured physiological parameters recorded.
• However, following the completion of the six-hour infusion period, there was a decrease noted in both the heart rate and average arterial pressure compared to the preinfusion measurements.
• Despite the experimentation, the researchers could not record any significant analgesic effect in the horses during or after the ketamine infusion.
• Upon inspection, it was observed that the pharmacokinetic variables did not vary noticeably between the two different dosages.

Conclusion

• The study concludes that ketamine can be administered continuously at a subanesthetic level, i.e., 0.4 or 0.8 mg/kg/h, to horses that are awake, without triggering any undesirable behavioral effects.
• The researchers also noted that the pharmacokinetic values derived from their study were different from those obtained from single-dose IV bolus administration of this drug, indicating that the method of administration can affect how the drug is processed in the body.