Cardiopulmonary and sedative effects of intravenous administration of low doses of medetomidine and xylazine to adult horses.

The study analyses the effects of sedative drugs medetomidine and xylazine on adult horses. The findings suggest both drugs cause similar levels of sedation and cardiopulmonary changes, although effects of medetomidine linger slightly longer.

Study Design and Methodology

• The researchers performed their study on ten healthy adult female horses. Half of these horses were administered with medetomidine, whereas the other half were given xylazine.
• The administered dosages were 4 micrograms/kg of body weight for medetomidine and 0.4 mg/kg for xylazine, both given intravenously.
• The team monitored various physiological parameters at regular intervals. These parameters included heart and respiratory rate, arterial and pulmonary arterial blood pressures, cardiac output, rectal temperature, and blood gas partial pressures.
• Ataxia (loss of control of body movements) and sedation scores were also recorded before the drug administration and every five minutes until an hour later.

Key Findings in Research

• The findings indicated that both medetomidine and xylazine caused a significant decrease in arterial blood pressure in horses.
• The cardiac output of the horses, compared to baseline values, decreased significantly at various intervals after the administration of medetomidine, but increased significantly after 40 and 60 minutes of giving xylazine.
• Despite a significant decrease in the respiratory rate in both groups, there was no significant change in the results of blood gas analyses over time, implying no major impact on the horse’s respiratory health.
• Sedation and ataxia effects had comparable levels in both groups, but horses given medetomidine exhibited slightly prolonged ataxia symptoms.
• Horses resumed eating hay between 10 to 55 minutes after drug administration.

Conclusions

• The research concluded that low, equipotent doses of medetomidine and xylazine induce comparable levels of ataxia and sedation in adult horses.
• There were similar cardiopulmonary changes in both groups. For example, arterial blood pressure decreased with both drugs while the cardiac output varied over time, suggesting these sedatives have considerable cardiovascular impacts.
• The significant finding was that both these sedatives spring back normal behavioral activity (like eating hay) in horses within an hour.