Abstract

The purpose of this study is to describe the pharmacokinetics of ceftiofur sodium (Naxcel, Pharmacia-Upjohn, Kalamazoo, MI 93065 USA) in the common green iguana (Iguana iguana) using the two most common routes of clinical administration of antibiotics in this species. Adult common green iguanas (n = 10) weighing between 1.2-6.6 kg, were studied (six males, four females). The iguanas were randomly assigned to two groups. All of the animals were maintained at 29.5°C, fed a commercial folivore ration, fresh produce, and had access to water at all times. Each iguana received 5 mg/kg ceftiofur sodium as an i.m. injection in the triceps muscle or as a s.c. injection over the scapula just lateral to the dorsal midline. In a second trial each animal received the reciprocal treatment. Heparinized blood samples were taken from the ventral tail vein at 0, 20, 40, 60, 120, 240, 480 min, and 24, 48, and 72 hr following ceftiofur sodium administration. Blood samples were held at 7°C until centrifuged. Plasma was separated from the cells by centrifugation for 10 min at 3600 rpm within 1 hr of collection. Plasma samples were frozen at ?70°C until assayed. Levels of ceftiofur sodium, desfuroylceftiofur, and desfuroylceftiofur conjugates were measured with high performance liquid chromatography (HPLC) as previously described.¹ Samples were plotted against time and analyzed with a commercial software program. P values < 0.01 were considered statistically significant. The results from this study show that kinetics of ceftiofur sodium in the common green iguana is best described by using a two-compartment model of an i.v. bolus infusion. Peak levels were reached in < 20 min by the i.m. route and in < 40 min via the s.c. route, demonstrating that this antibiotic is rapidly absorbed via the two routes investigated. The terminal average half-life of ceftiofur sodium via the i.m. route was 15.7 ± 4.7 (SD) hr, whereas the average half-life was 18.5 ± 6.0 (SD) hr by the s.c. route. Both of these values were statistically equivalent. The average areas under the curve (AUC), a measurement of bioavailability, were equivalent at 11,722 ± 7907 (SD) µg hr/ml for i.m. and 12143 ± 9633 (SD) ?hr/ml for s.c. injections. The maximum average concentration reached was significantly higher with the i.m. route in comparison to the s.c. route (28.6 ± 8.0 [SD] µg/ml and 18.6 ± 8.3 [SD] µg/ml, respectively). Utilizing both routes of administration, ceftiofur sodium levels were maintained at or above 2 µg/ml for > 33 hr, suggesting that the routes were clinically equivalent. Ceftiofur sodium is an acceptable alternative antibiotic in the common green iguana. Peak concentrations of ceftiofur sodium were different for the two administration routes, but the bioavailability was equivalent. A reasonable dosing schedule for ceftiofur sodium (5 mg/kg i.m. or s.c.) in the common green iguana for microbes susceptible at 2 µ/ml would occur every 24 hr.

Acknowledgments

We thank the Center for Companion Animal Health, School of Veterinary Medicine, University of California-Davis and the Pharmacia-Upjohn Co. for their generous financial support. We also appreciate the assistance of the keeper staff of the San Diego Zoo veterinary and reptile departments and the hospital technical staff with their care, maintenance, and restraint of the animals, and Mr. Scott Wetzlich for his assistance with the HPLC analysis

References

1.  Jaglan PS, BL Cox, TS Arnold, MF Kubicek, DJ Stuart, TJ Gilbertson. 1990 Liquid chromatographic determination of desfuroylceftiofur metabolite of ceftiofur as residue in cattle plasma. J. Assoc. Off. Anal. Chem. 73: 26-30.