Pharmacokinetics and pharmacodynamics of intravenous romifidine and propranolol administered alone or in combination for equine sedation.

This research examines the impacts of administering propranolol, romifidine, or a combination of both, on sedation, physiological responses, and behavioral responsiveness in horses. The findings indicate that while propranolol doesn’t reduce behavioral responsiveness or sedation alone, it does enhance romifidine sedation. Yet, this combination also increases the chance of severe bradycardia.

Objective of the Study

• The study primarily aims to conduct an in-depth inquiry into the pharmacokinetics and pharmacodynamics of propranolol, romifidine, and a mix of both. Its goal is to discern their sedation efficacy and potential side effects in horses, both when dispensed together and separately.

Methodology

• In a randomized, crossover study, the research utilizes six mature horses. Treatment includes administering propranolol or romifidine separately or in conjunction, with a minimum of one week between treatments.
• Behavioural responsiveness, alertness, physiological variables are measured before and up to 960 minutes post administration of the drug treatments. Blood collection was also conducted for blood gas and acid-base examinations as well as measuring plasma drug concentrations.

Results

• The results showed that systemic clearance reduced and there was a considerable increase in the concentration-time curve’s area for both drugs in combination, as opposed to their separate administration.
• The combination of propranolol and romifidine and romifidine alone both led to a decrease in behavioral responsiveness and induced sedation, lasting up to 240 and 480 minutes respectively. The sedation was deeper within the first 16 minutes of administering the combined treatment.
• All treatments resulted in a significant heart rate decrease for at least 60 minutes. The combined treatment also significantly increased the incidence of severe bradycardia (<20 beats minute).

Conclusions

• The research concludes that propranolol, while not affecting behavioral responsiveness or sedation when dispensed alone, augments romifidine sedation in horses when administered together. However, this combination treatment significantly increases the risk of severe bradycardia, necessitating caution in co-administration of these drugs at the studied doses.