Intravenous tramadol: effects, nociceptive properties, and pharmacokinetics in horses
Article first published online: 15 OCT 2009
© 2009 The Authors. Journal compilation © 2009 Association of Veterinary Anaesthetists
Veterinary Anaesthesia and Analgesia
Volume 36, Issue 6, pages 581–590, November 2009
How to Cite
Dhanjal, J. K., Wilson, D. V., Robinson, E., Tobin, T. T. and Dirokulu, L. (2009), Intravenous tramadol: effects, nociceptive properties, and pharmacokinetics in horses. Veterinary Anaesthesia and Analgesia, 36: 581–590. doi: 10.1111/j.1467-2995.2009.00492.x
- Issue published online: 15 OCT 2009
- Article first published online: 15 OCT 2009
- Received 24 July 2008; accepted 31 December 2008.
Vol. 39, Issue 6, 610, Article first published online: 5 OCT 2012
Objective To determine the optimal dose, serum concentrations and analgesic effects of intravenous (IV) tramadol in the horse.
Study design Two-phase blinded, randomized, prospective crossover trial.
Animals Seven horses (median age 22.5 years and mean weight 565 kg).
Methods Horses were treated every 20 minutes with incremental doses of tramadol HCl (0.1–1.6 mg kg−1) or with saline. Heart rate, respiratory rate, step frequency, head height, and sweating, trembling, borborygmus and head nodding scores were recorded before and up to 6 hours after treatment. In a second study, hoof withdrawal and skin twitch reflex latencies (HWRL and STRL) to a thermal stimulus were determined 5 and 30 minutes, and 1, 2, 4 and 6 hours after bolus IV tramadol (2.0 mg kg−1) or vehicle. Blood samples were taken to determine pharmacokinetics.
Results Compared to saline, tramadol caused no change in heart rate, step frequency or sweating score. Respiratory rate, head height, and head nodding and trembling scores were transiently but significantly increased and borborygmus score was decreased by high doses of tramadol. Following cumulative IV administration of 3.1 mg kg−1 and bolus IV administration of 2 mg kg−1, the elimination half-life of tramadol was 1.91 ± 0.33 and 2.1 ± 0.9 hours, respectively. Baseline HWRL and STRL were 4.16 ± 1.0 and 3.06 ± 0.99 seconds, respectively, and were not significantly prolonged by tramadol.
Conclusion and clinical relevance IV tramadol at cumulative doses of up to 3.1 mg kg−1 produced minimal transient side effects but 2.0 mg kg−1 did not provide analgesia, as determined by response to a thermal nociceptive stimulus.