Abstract
This study investigated the use of behavioral monitoring to determine the presence or absence of pain and efficacy of pain therapy administered to a Florida manatee critically injured by a boat strike. The study subject was a 4-year-old Florida manatee (Trichechus manatus latirostris) undergoing rehabilitative care for a severed and displaced spinal column at the Miami Seaquarium. Tramadol, a pain medication commonly used in veterinary medicine, was administered for a period of 7 weeks, while a behavioral ethogram was developed and used to determine whether drug administration was associated with specific behaviors, including increases and decreases in activity.1,3,4,6 Serum samples were collected, to determine a brief pharmacokinetic overview, from the subject to determine the pharmacokinetics of Tramadol in the Florida manatee to better understand the rate of absorption, distribution, and duration of the drug's efficacy. The results of the study indicated that 100 mg (1 mg/kg) of Tramadol was an effective dosage for the Florida manatee, and 3.5 hours after ingestion the drug was identified at a concentration of 21 ng/ml for Tramadol and 7 ng/ml for M1, a metabolite of Tramadol, without producing potentially dangerous side effects such as intestinal upset. Serum samples collected 22 hours after initial ingestion of the dosage identified no detectable levels of the medication, indicating that Tramadol administered at this particular dosage must be provided daily to maintain efficacy. Twenty-six behaviors were evaluated during the course of the study. Results of behavioral observations indicated that there was a significant increase in both the frequency and duration of the behaviors "resting on bottom of pool" and "crunch" while not receiving pain medication when compared to receiving Tramadol, and both of these behaviors may be indicative of a pain response.3,4,6 Thus, the results of this study indicated that Tramadol administered in specific dosages may be effective in mitigating pain in manatees, and a behavioral ethogram may be a valuable, non-invasive tool for use in assessing pain in the Florida manatee, a Federally- and state-listed endangered species.2,4,5 Samples also taken from two separate marine mammal species (Zalophus californianus and Tursiops truncatus) receiving Tramadol allowed for an opportunistic comparison of the pharmacokinetic levels in these species to the Florida manatee.
Acknowledgements
The authors would like to thank the staff of the Miami Seaquarium for their help and specifically Leah Brewer for her invaluable assistance on this project. We would also like to thank Dr. Sherry Cox, Pharmacology Laboratory Director at the University of Tennessee, College of Veterinary Medicine and her staff for processing the samples used for this project.
References
1. Asher L, Collins LM, Ortiz-Pelaez A, Drewe JA, Nicol CJ, Pfeiffer DU. Recent advances in the analysis of behavioural organization and interpretation as indicators of animal welfare. J R Soc Interface. 2009;6(41):1103–1119.
2. Bufalari A, Adami C, Angeli G, Short CE. Pain assessment in animals. Vet Res Commun. 2007;31(Suppl 1):55–58.
3. Price J, Catriona S, Welsh EM, Waran NK. Preliminary evaluation of a behavior-based system for assessment of post-operative pain in horses following arthroscopic surgery. Vet Anesth Analg. 2003;30(3):124–137.
4. Stubsjøen SM, Flø AS, Moe RO, Janczak AM, Skjerve E, Valle PS, et al. Exploring non-invasive methods to assess pain in sheep. Physiol Behav. 2009;98(5):640–648.
5. Souza M, Cox SK. Tramadol use in zoologic medicine. Vet Clin North Am Exot Anim Pract. 2011;14(1):117–130.
6. Walker KA, Horning M, Mellish JE, Weary DM. The effects of two analgesic regimes on behavior after abdominal surgery in Steller sea lions. Vet J. 2011;190(1):160–164.