Sedative and analgesic effects of intravenous xylazine and tramadol on horses

Abstract

This study was performed to evaluate the sedative and analgesic effects of xylazine (X) and tramadol (T) intravenously (IV) administered to horses. Six thoroughbred saddle horses each received X (1.0 mg/kg), T (2.0 mg/kg), and a combination of XT (1.0 and 2.0 mg/kg, respectively) IV. Heart rate (HR), respiratory rate (RR), rectal temperature (RT), indirect arterial pressure (IAP), capillary refill time (CRT), sedation, and analgesia (using electrical stimulation and pinprick) were measured before and after drug administration. HR and RR significantly decreased from basal values with X and XT treatments, and significantly increased with T treatment (p < 0.05). RT and IAP also significantly increased with T treatment (p < 0.05). CRT did not change significantly with any treatments. The onset of sedation and analgesia were approximately 5 min after both X and XT treatments; however, the XT combination produced a longer duration of sedation and analgesia than X alone. Two horses in the XT treatment group displayed excited transient behavior within 5 min of drug administration. The results suggest that the XT combination is useful for sedation and analgesia in horses. However, careful monitoring for excited behavior shortly after administration is recommended.

Fig. 1

Sedation score in response to intravenous administration of xylazine (X), tramadol (T), and xylazine plus tramadol (XT). ^a,b,cSignificant differences (p < 0.05) from baseline (time = 0) value for each drug. ^*Significant differences (p < 0.05) between T and X. ^† Significant differences (p < 0.05) between T and XT. ^‡ Significant differences (p < 0.05) between X and XT. Sedation score is expressed using a 4-point scale and each value represents the means ± SD.

Fig. 2

Analgesia score with electro-stimulation in response to intravenous administration of xylazine (X), tramadol (T), and xylazine plus tramadol (XT). ^a,b,cSignificant differences (p < 0.05) from baseline (time = 0) value for each drug. ^*Significant differences (p < 0.05) between T and X. ^†Significant differences (p < 0.05) between T and XT. ^‡Significant differences (p < 0.05) between X and XT. Analgesic score of electrical stimulation is expressed using a 4-point scale and each value represents the means ± SD.

Fig. 3

Analgesia score with pinprick in response to intravenous administration of xylazine (X), tramadol (T), and xylazine plus tramadol (XT). ^a,b,cSignificant differences (p < 0.05) from baseline (time = 0) value for each drug. ^*Significant differences (p < 0.05) between T and X. ^†Significant differences (p < 0.05) between T and XT. Significant differences between X and XT were not detected. Analgesic score of pinprick is expressed by the sum (0 to 12) of a 4-point scale of three sites (right neck, right paralumbar fossa, and right hip) and each value represents the means ± SD.