Abstract

Many zoos and aquariums house various species of elasmobranchs, but there remains a paucity of data with regards to the pharmacokinetics of drugs, including antibiotics, in these animals. Whitespotted bamboo sharks (Chiloscyllium plagiosum) are a small, demersal, tropical species commonly found in aquariums worldwide. Despite their popularity in managed collections and the common usage of antimicrobials to treat bacterial infections, there are few peer-reviewed studies regarding antibiotic usage in this species, and dosages are often extrapolated from teleosts. Pharmacokinetics of danofloxacin, a synthetic veterinary fluoroquinolone antibiotic, have been evaluated in various teleost species, showing a long elimination half-life, high bioavailability, and good tissue penetration.^1-5 Anecdotally, it is used in elasmobranch species as well, but to the authors’ knowledge, there have been no published studies investigating the pharmacokinetics of danofloxacin in elasmobranchs. The goal of this study was to determine the pharmacokinetics of a single intramuscular 10 mg/kg dose of danofloxacin in 24 whitespotted bamboo sharks.

All sharks were clinically healthy based on behavior and physical exam, and no negative side effects were seen throughout the course of the study following danofloxacin administration. Blood samples were collected from the caudal tail vein, with four blood samples collected from each individual shark. A sparse sampling method was applied, with samples collected from six sharks at 0, 0.25, 0.5, 1, 2, 4, 6, 8, 12, 24, 36, 48, 72, 96, 120, and 144 hours after administration. Concentrations of danofloxacin in plasma were determined using liquid chromatography tandem mass spectrometry (LC-MS/MS) and pharmacokinetic parameters were determined using noncompartmental analysis. Maximum plasma concentration (mean 4,921.1 ng/ml) was reached by the first sampling time point of 15 minutes, indicating rapid absorption, with a half-life (t_½) of 25.5 hours. The drug was detected in all plasma samples at all time points, with suitable plasma concentrations at 144 hours to inhibit pathogens with MIC values below 0.016 µg/ml. The results of this study support administering danofloxacin every 6 days at a dose of 10 mg/kg IM to treat susceptible bacterial isolates.

Acknowledgements

The authors wish to thank the UC Davis Aquatic Animal Health Fellowship and the Aquarium of the Pacific (AoP) for supporting this project. The authors would also like to thank the AoP Molina Animal Care Center veterinary technicians and veterinary volunteers for their help in the collection of the samples.

*Presenting author
+Student presenter

Literature Cited

1.  Aboubakr M, Soliman A. Pharmacokinetics of danofloxacin in African catfish (Clarias gariepinus) after intravenous and intramuscular administrations. Acta Veterinaria Hungarica. 2019;67(4):602–609.

2.  Corum O, Durna Corum D, Er A, Terzi E, Uney K. Plasma and tissue disposition of danofloxacin in brown trout (Salmo trutta fario) after intravenous and intramuscular administrations. Food Addit Contam Part A Chem Anal Control Expo Risk Assess. 2018;35(12):2340–2347.

3.  Parker-Graham CA, Siniard WC, Byrne BA, Knych HK, Soto E. Pharmacokinetics of danofloxacin following intramuscular administration of a single dose in koi (Cyprinus carpio). Am J Vet Res. 2020;81(9):708–713.

4.  Song ZW, Yang F, Dai Y, Zhang CS, Shao HT, Wang H, Ma KL, Li ZE, Yang F. Population pharmacokinetics of danofloxacin in Yellow River carp (Cyprinus carpio haematopterus) after one single oral dose. Front Vet Sci. 2022;9:1–9.

5.  Terzi E, Corum O, Bilen S, Kenanoglu ON, Atik O, Uney K. Pharmacokinetics of danofloxacin in rainbow trout after different routes of administration. Aquaculture. 2020;520:1–6.