Itraconazole plasma and tissue concentrations in the spiny lizard (Sceloporus sp.) following once-daily dosing

Mycotic infections in reptiles present as primary diseases and as secondary problems in healing wounds and immunocompromised animals. A triazole antimycotic drug, itraconazole is orally active and well distributed and is effective against many common fungal pathogens in humans. To assess plasma and tissues concentrations after oral dosing in reptiles, a 23.5-mg/kg (mean) itraconazole dose was administered orally with a standard food bolus once daily for 3 days to 10 groups of three or four spiny lizards (Sceloporus sp.). On days 0, 1, 2, 3, 4, 6, 9, 12, and 18, group samples of blood, liver, and muscle were collected. Microbiologic assay of itraconazole concentrations was performed on these pooled samples. Values from an elimination graph of the concentrations of area under the curve (377.21 micrograms.hr/ml) and terminal elimination half-life (48.3 hr) were obtained for itraconazole in spiny lizard plasma. Peak itraconazole concentration of 2.48 micrograms/ml was obtained in two half-lives and would be expected to achieve steady state at approximately 3.1 micrograms/ml plasma concentration in 10 days. Peak liver concentration of 4.27 micrograms/ml was attained in 89.95 hr. Muscle concentration did not exceed 0.63 micrograms/ml and declined by 97.3 hr. With this dosing regimen, itraconazole plasma and liver concentrations would persist within reported minimum inhibitory concentrations for many fungal pathogens for 6 days beyond the peak concentration.