Evaluation of Tissue Concentrations and Liver Histopathology Following Single and Multiple Doses of Itraconazole via Immersion Bath in Panamanian Golden Frogs (Atelopus zeteki)

Itraconazole is an antifungal drug used to treat chytridiomycosis, one of the leading causes of global amphibian decline in species such as the critically endangered Panamanian golden frog (Atelopus zeteki). Despite its widespread use for prophylaxis and treatment in both assurance colonies and free-ranging amphibians, there is minimal pharmacologic information to guide dosing. In experiment A, frogs were exposed to 0.01% itraconazole for 10 min and tissue samples were analyzed at various time points from 1 to 84 h. In experiment B, frogs were divided into six groups and exposed to itraconazole in different combinations of concentration (0.01% or 0.001%) and time (5, 10, or 15 min) over 10 days of treatment. Tissue concentrations were quantified via high-performance liquid chromatography. In experiment A, following a one-time dose, itraconazole concentrations remained high until the end of the experiment at 84 h. In experiment B, at 0.01% itraconazole daily for 10 days, skin and liver concentrations were high and increased substantially over the 10-day treatment course. Frogs exposed at the lower concentration (0.001%) had tissue concentrations that appeared to remain steady. At the reported doses over 10 days, there was no histologic evidence of hepatic toxicity, although one frog was found dead in the low-dose bath at 84 h and could not be further analyzed. This experiment is an excellent example of assurance colonies providing evidence-based information for the improved care and welfare of amphibians in order to prepare for future free-ranging populations.