Clarithromycin pharmacokinetics in the desert tortoise (Gopherus agassizii)

Area of Science:

• Veterinary Pharmacology
• Herpetology
• Antimicrobial Pharmacokinetics

Background:

• Clarithromycin is an orally administered macrolide antibiotic effective against Mycoplasma species.
• Desert tortoises (Gopherus agassizii) are susceptible to Mycoplasma infections, necessitating effective treatment strategies.
• Understanding drug pharmacokinetics is crucial for optimizing therapeutic efficacy and safety in reptiles.

Purpose of the Study:

• To determine the single-dose and multidose pharmacokinetic parameters of clarithromycin in desert tortoises.
• To evaluate the potential for drug accumulation with repeated oral administration.
• To establish appropriate dosing regimens for treating Mycoplasma infections in this species.

Main Methods:

• Oral administration of clarithromycin at 7.5 mg/kg and 15 mg/kg to desert tortoises.
• Measurement of plasma drug concentrations over 72 hours post-administration.
• Application of noncompartmental pharmacokinetic analyses (Bayesian, expectation maximization, linear regression).

Main Results:

• Single-dose pharmacokinetics at 15 mg/kg showed a Tmax of 8.0 hr, Cmax of 1.37 µg/mL, and t1/2 of 11.69 hr.
• Multidose studies indicated significant drug accumulation, with a slower elimination rate (t1/2 ≈ 30.52 hr).
• Predicted optimal dosing adjusted to 15 mg/kg every 2-3 days to maintain therapeutic levels (2-7.5 µg/mL).

Conclusions:

• Clarithromycin exhibits dose-dependent pharmacokinetics and accumulates with repeated oral dosing in desert tortoises.
• Single-dose pharmacokinetic data may overestimate the required dosing frequency.
• Oral clarithromycin shows potential for treating Mycoplasma infections in reptiles, but careful dose adjustment is necessary.