Pharmacokinetics of Butorphanol Delivered Via Osmotic Pump Over Seven Days to Common Peafowl (Pavo cristatus)
Abstract
Avian pain management is particularly challenging due to the limited selection of effective medications and the frequency required for sufficient dosing. Commercially available osmotic pumps are implants that deliver a constant rate of medication using the osmotic gradient of the patient’s interstitial fluid. Initially developed for laboratory research, recent studies have validated their use in zoo and exotic animal practice.4-7 This study evaluated the utility of these pumps to deliver butorphanol continuously to common peafowl (Pavo cristatus). Twelve adult males were anesthetized for surgical implantation of two osmotic pumpsa containing butorphanolb (2 ml each pump, 40–45 mg/ml, 247 µg/kg/h). Pumps were removed under anesthesia 168 h later. Blood was collected just prior to implantation, at 3, 6, 12, 24, 48, 72, 96, 120, 144, and 168 h post-implantation, and at 3 and 6 h post-removal. Plasma butorphanol levels were measured via high-performance liquid chromatography. Results showed a peak in plasma levels at 24 h (98.3±19.6 ng/ml) with a steady state of butorphanol (mean=83.0±16.7 ng/ml) throughout the week. Plasma levels are similar to previously established analgesic levels in avian patients.3 Following pump removal, butorphanol was rapidly cleared (half-life=1.44±0.43 h). Clearance (3.9 l/kg/h) was similar to chickens2 and raptors.1 This study establishes a safe, effective, and practical method for managing pain continuously in post-surgical or acute trauma avian cases without the need for frequent dosing or handling. Dosages using different models of the pumps can be extrapolated from this dataset to improve postoperative care for other avian species.
Endnotes
a. Alzet® 2ML1 pump (DURECT Corp., Cupertino, CA, USA; www.alzet.com), 2-ml fill volume, pump rate 10 µl/h, duration 7 d
b. ZooPharm, Windsor, CO, USA
Acknowledgments
The authors thank the AAZV Zoological Medicine and Wildlife Health Research Grant for funding of this project. The authors would also like to recognize the efforts of Mr. Matt Warner for assistance in sample testing, and the staff of the Zoological Health Program and Ornithology Department for assistance in animal care and sample collection.
Literature Cited
1. Riggs SM, Hawkins MG, Craigmill AL, Kass PH, Stanley SD, Taylor IT. Pharmacokinetics of butorphanol tartrate in red-tailed hawks (Buteo jamaicensis) and great horned owls (Bubo virginianus). Am J Vet Res. 2008;69:596–603.
2. Singh PM, Johnson C, Gartrell B, Mitchinson S, Chambers P. Pharmacokinetics of butorphanol in broiler chickens. Vet Rec. 2011;168:588–591.
3. Sladky KK, Krugner-Higby L, Meek-Walker E, Heath TD, Paul-Murphy J. Serum concentrations and analgesic effects of liposome-encapsulated and standard butorphanol tartrate in parrots. Am J Vet Res. 2006;67:775–781.
4. Sykes JM, Folland D, Bemis D, Ramsay EC. Osmotic pump delivery of florfenicol or amikacin in Mojave rattlesnakes (Crotalus scutulatus) with Salmonella arizonae osteomyelitis. In: Proc 15th Annu Conf Assoc Reptilian Amphibian Vet; 2008:29–30.
5. Sykes J, Georoff T, Rodriguez C. Combination of systemic and local treatment of an infected bite wound using an osmotic pump in a gelada (Theropithecus gelada). In: Proc 38th Annu Workshop Am Primate Vet; 2010.
6. Sykes JM, Ramsay EC, Schumacher J, Daniel GB, Cox S, Papich M. Evaluation of an implanted osmotic pump for delivery of amikacin to corn snakes (Elaphe guttata guttata). J Zoo Wildl Med. 2006;37:373–380.
7. Sykes JM, Cox S, Ramsay EC. Evaluation of an osmotic pump for fentanyl administration in cats as a model for nondomestic felids. Am J Vet Res. 2009;70:950–955.