Clinical pharmacokinetics of tramadol and main metabolites in horses undergoing orchiectomy.

The study explores the pharmacokinetics of a synthetic codeine analogue, Tramadol, in horses. The researchers administered the drug to horses prior to surgery and monitored its concentration and metabolites in the bloodstream and urine. They concluded that the drug could potentially be safe and effective for pain relief in horses undergoing surgery.

Objective

• The study was aimed at investigating the serum pharmacokinetic profile and urinary excretion of tramadol and its metabolites in horses. The researchers also evaluated the degree of cardiovascular stability and the intraoperative effect and postoperative analgesia in horses undergoing orchiectomy (castration).

Methods

• Tramadol was administered intravenously to eight male yearling horses as a bolus over 60 seconds, 5 minutes after intubation and 15 minutes prior to surgery.
• Drug quantification was performed in serum and urine for tramadol and its metabolites (O-desmethyltramadol [M1], N-desmethyltramadol [M2] and N,O-desmethyltramadol [M5]) by high-performance liquid chromatography with fluorimetric detection. This is a technique widely recognized for its accuracy in separating and quantifying drugs and their metabolites.

Results

• The mean tramadol concentration detected 0.08 hours after administration was 14.87 ± 11.14 μg/mL, which decreased to 0.05 ± 0.06 μg/mL at 10 hours post-administration.
• For M1 and M2, the median maximum concentration (Cmax) and time to achieve maximum concentration (Tmax) were 0.05 μg/mL and 0.75 hours, and 0.08 μg/mL and 2 hours respectively.
• M5, the third metabolite, was never detected. In urine, tramadol was found to be the most detected compound, followed by M1 and M2, and then M5.

Conclusion

• The researchers concluded that tramadol did not cause any adverse effects and based on their findings, it could potentially be a safe and effective analgesic for horses undergoing surgery. However, it’s noteworthy that the study was done on a small sample size, limiting the general applicability and robustness of their findings.