OBJECTIVE To compare absorption characteristics of orally administered compounded itraconazole capsules and suspension with those of reference (brand-name) formulations in healthy cats. DESIGN Randomized crossover study. ANIMALS 8 healthy adult cats. PROCEDURES After 12 hours of food withholding, cats received 50 mg of itraconazole (reference capsule, reference solution, compounded capsule, and compounded suspension) in a randomized crossover design, with a 21-day washout period. Capsules were administered with a small meal. Blood samples were collected at predetermined intervals for high-pressure liquid chromatography analysis of plasma itraconazole concentrations. Area under the concentration-time curve, maximum concentration, and terminal half-life of itraconazole were determined and compared among formulations. RESULTS 7 cats completed the study. Mean half-life of itraconazole in reference formulations was 18 to 26 hours. Absorption of the reference solution was 3 times that of the reference capsule. Compounded formulations were absorbed poorly and inconsistently. Complete pharmacokinetic results for the compounded capsule were obtained for only 3 of 6 cats and for the compounded suspension for only 1 of 5 cats, precluding bioequivalence analysis. Relative absorption of compounded formulations was only 2% to 8% of reference formulation values. CONCLUSIONS AND CLINICAL RELEVANCE Compounded oral formulations of itraconazole should not be used for cats because of poor absorption. The differences in absorption between the 2 reference formulations suggested that doses required to meet human target serum concentrations in cats are markedly different (capsules, 12.5 mg/kg [5.7 mg/lb], q 24 h, with food; solution, 4 mg/kg [1.8 mg/lb], q 24 h, without food).

BackgroundPosaconazole is the most active available azole antifungal drug, but absorption and pharmacokinetics are not available to guide dosing regimens in cats.ObjectiveTo determine the pharmacokinetics of posaconazole in cats given an IV solution and PO suspension.AnimalsSix healthy, adult research cats.MethodsAfter a 12‐hour fast, each cat received 15 mg/kg of posaconazole PO suspension with food. Four cats also received 3 mg/kg IV posaconazole after a 7‐day washout period. Plasma was collected at predetermined intervals for analysis using high‐pressure liquid chromatography (HPLC). Concentration data were analyzed using a 2‐compartment pharmacokinetic analysis for IV administration data and a 1‐compartment analysis with first‐order input for PO administration data using Phoenix® software.5 ResultsAfter IV dosing, volume of distribution (V SS) was 1.9 (0.3) L/kg (mean, standard deviation), terminal half‐life (T ½) was 57.7 (28.4) hours, and clearance was 28.1 (17.3) mL/kg/h. After PO dosing, peak concentration (C MAX) was 1.2 (0.5) μg/mL and T ½ was 38.1 (15.0) hours. Bioavailability of PO suspension was 15.9% (8.6). No adverse effects were observed with either route of administration.Conclusion and Clinical ImportanceDespite low PO absorption, these data allow for simulation of PO dosage regimens that could be explored in clinical studies. Two regimens can be considered to maintain targeted trough concentrations of 0.5–0.7 μg/mL as extrapolated from studies in humans: (1) 30 mg/kg PO loading dose followed by 15 mg/kg q48h, or (2) 15 mg/kg PO loading dose followed by 7.5 mg/kg q24h.