Pharmacokinetic Study of Orally Administered Tramadol in California Sea Lions (Zalophus californianus)
Abstract
California sea lions (Zalophus californianus), both wild and in captivity, present for many conditions in which pain control medications may be indicated. Tramadol is an analgesic drug that can be easily administered orally to California sea lions by placing it into fish. Tramadol and its major metabolite O-desmethyltramadol (M1) are agonists of the mu opioid receptor and also act on the serotonin, and norepinephrine pathways, with minimal adverse effects.1
In this study, the pharmacokinetics of tramadol and its major metabolite O-desmethyltramadol (M1) were determined for the California sea lion. A single dose was administered orally at 2 mg/kg to 12 wild California sea lions admitted for rehabilitation. Blood samples were then obtained at various points from ten minutes to 24 hours following administration of the drug. No more than two blood samples were obtained from each sea lion. Blood plasma was separated and stored at -80°C until analysis with high-performance liquid chromatography was performed to determine levels of tramadol and M1, the major active metabolite.
The pilot study results have shown that both tramadol and M1, the major active metabolite, are cleared from the plasma within 24 hours. The remaining samples in this study still need to be evaluated.
Acknowledgements
The authors would like to thank all of the staff and volunteers at The Marine Mammal Center who helped to make this project possible, especially the technicians that coordinated the sample scheduling, collection, and processing. All animal handling was conducted under procedures approved by TMMC Institutional Animal Care and Use Committee. Funding for travel to conduct the pilot study portion of this project was provided by John G. Shedd Aquarium. The sample matrix design was created by Dr. Tomas Martin-Jimenez, and all samples were analyzed at the pharmacology laboratory of Sherry Cox, University of Tennessee, CVM.
* Presenting author
Literature Cited
1. Grond S, Sablotzki A. 2004. Clinical pharmacology of tramadol. Clin Pharmacokinet. 43(13):879–923.