Plasma concentrations of terbinafine in Kemp’s ridley sea turtles (Lepidochelys kempii) peak at 24 hours after a single oral dose

Objective: To determine the pharmacokinetic parameters of a single dose of terbinafine administered orally to Kemp's ridley sea turtles (Lepidochelys kempii). Methods: In the spring of 2025, convalescent juvenile Kemp's ridley sea turtles that were undergoing rehabilitation due to cold stunning in Quincy, Massachusetts, were given 20 mg/kg terbinafine orally in a food item. Samples were collected via a sparse-sampling protocol from 0 to 120 hours after drug administration. Plasma drug concentrations were determined via reverse-phase HPLC. Pharmacokinetic parameters were determined using noncompartmental analysis for sparse data. Results: 15 turtles were included in this study. Terminal half-life was 24.1 hours, maximum plasma concentration was 1.17 µg/mL, time to maximum plasma concentration was 24 hours, area under the plasma concentration-versus-time curve from time 0 to the last point was 51.1 h•µg/mL, area under the plasma concentration-versus-time curve from time 0 to infinity was 53.8 h•µg/mL, and the percentage of the area under the plasma concentration-versus-time curve from time 0 to infinity extrapolated to infinity was 5.06%. Conclusions: Terbinafine plasma concentrations reached time to maximum plasma concentration at 24 hours and exceeded the MIC for several fungal pathogens that have previously been documented for Kemp's ridley sea turtles. Clinical Relevance: The results of this study can inform the treatment of fungal infections in Kemp's ridley sea turtles. Additional studies are warranted to assess plasma and tissue concentrations after multiple terbinafine doses in order to determine appropriate dosage frequency.