Effects of compounding on pharmacokinetics of itraconazole in black-footed penguins (Spheniscus demersus)

Itraconazole is used to treat and prevent aspergillosis in captive penguin colonies. Although commercial formulations of itraconazole are available, compounding is sometimes performed to decrease cost or to provide a different concentration of the drug. Using a two-way crossover design, the pharmacokinetics of both a commercially available oral itraconazole solution and a compounded oral itraconazole solution were compared in six black-footed penguins (Spheniscus demersus). Each itraconazole formulation was administered orally in frozenthawed capelin at 7 mg/kg. Plasma itraconazole concentrations at time 0 (pretreatment), 20 and 40 min postdrug administration, and 1, 2, 4, 6, 8, and 12 hr postdrug administration were determined using reverse-phase high-performance liquid chromatography. Drug concentrations were analyzed using standard pharmacokinetic methods. Plasma clearance of the commercial itraconazole solution was more rapid than the clearance published for other species, possibly warranting more frequent dosing in black-footed penguins. Absorption of itraconazole, as determined by peak concentration and area under the curve, was significantly higher for the commercial formulation when compared to the compounded formulation, likely as a result of the presence of cyclodextrin, a carrier compound shown to improve oral absorption, in the commercial formulation. Extrapolating dosing regimens for compounded itraconazole formulations from regimens determined for commercial formulations warrants caution as a result of the significant differences in pharmacokinetics.