Jungers

Pharmacokinetic Analysis of Ceftazidime in Signal Crayfish (Pacifastacus leniusculus) Following Intravascular and Intramuscular Administration

1Hali T. Jungers, 2Heather K. Knych, 1Taylor N. Abraham, 1Taylor I. Heckman, 1Eva M. Quijano Cardé, 1Zeinab Yazdi, 1Diem Thu Nguyen, 1Isabella Medina Silva, 3Lana Krol, 3Freeland H. Dunker, 4Eileen E. Henderson, 1Esteban Soto

1Department of Medicine & Epidemiology, School of Veterinary Medicine, University of California Davis, Davis, CA 95616; 2K.L. Maddy Equine Analytical Pharmacology Laboratory, School of Veterinary Medicine, University of California Davis, Davis, CA 95616; 3Steinhart Aquarium at California Academy of Sciences, San Francisco, CA 94118; 4California Animal Health and Food Safety Laboratory (San Bernardino) University of California Davis, 105 W. Central Avenue, San Bernardino, CA 92408

ABSTRACT

Crustaceans are becoming increasingly popular as pets and are housed by many aquatic and zoological institutions. When disease occurs involving shell lesions, often implicating bacterial infections, clinicians typically implement treatment plans that include empirical antibiotic therapy. Unfortunately, few controlled studies have been done to assess common broad spectrum antibiotics such as ceftazidime, which are used in aquatic animal medicine. Therefore, this study aimed to determine and compare the pharmacokinetics of a single 22 mg/kg dose of ceftazidime following intravascular (IV) and intramuscular (IM) administration in signal crayfish (Pacifastacus leniusculus). A total of 198 wild caught, signal crayfish were obtained from a local vendor and used as part of this research study. Six crayfish were haphazardly selected and designated as untreated, negative controls. Twelve served as route of administration controls (six crayfish for each route) and were injected with an equivalent quantity of sterile water. The remaining 180 crayfish were assigned to 30 ceftazidime treatment groups with 6 animals/group and 15 timepoints (5, 15, 30, and 45 minutes and 1, 2, 6, 12, 24, 36, 48, 72, 120, 168, and 240 hours post ceftazidime administration). Crayfish were given a single dose of ceftazidime (22 mg/kg) either IV by access of the joint between the carpus and merus or IM in the ventral tail musculature. Hemolymph samples were collected from the ventral tail vasculature of each group at the appropriate timepoint. Plasma drug concentrations were determined by liquid chromatography with tandem mass spectrometry using a noncompartmental pharmacokinetic model of a sparse data set. The maximum ceftazidime plasma concentration for IM injection (124.6 ± 14.7 mg/mL) was reached approximately 5 minutes after ceftazidime administration, with approximately 80% bioavailability. The hemolymph terminal half-life was 10.2 and 8.03 hours after IV and IM administration, respectively. Ceftazidime was last detected at 120 and 72 hours after IV and IM administration, respectively. Results suggest that ceftazidime reaches a maximum plasma concentration quickly and has good bioavailability when administered IM. For crustaceans undergoing antibiotic treatment, an IV route could be considered due to its longer half-life but if this is not feasible, IM administration remains a good option.

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