Pharmacokinetics of fluconazole after oral administration to healthy beagle dogs

A single-blind randomised study comparing the efficacy of fluconazole and itraconazole for the treatment of Malassezia dermatitis in client-owned dogs

BACKGROUND

No reports have compared the clinical therapeutic efficacy of fluconazole and itraconazole in canine Malassezia dermatitis.

OBJECTIVES

The study aimed to compare the clinical therapeutic efficacy of fluconazole and itraconazole and to evaluate the adverse effects of fluconazole in canine Malassezia dermatitis.

ANIMALS

Sixty-one client-owned dogs with Malassezia dermatitis.

MATERIALS AND METHODS

The enrolled animals were randomly divided into groups receiving 5 mg/kg fluconazole (5FZ), 10 mg/kg fluconazole (10FZ) or 5 mg/kg itraconazole (5IZ). The drugs were orally administered once daily for 28 days. Cytological examination, clinical index score (CIS), pruritus Visual Analog Scale (PVAS) evaluation and blood analysis (for 5FZ only) were performed on Day (D)0, D14 and D28.

RESULTS

On D14, significant reductions in mean yeast count (MYC), CIS and PVAS were observed in the 5FZ (n = 20, p < 0.01), 10FZ (n = 17, p < 0.01) and 5IZ (n = 16, p < 0.05) groups. In all three groups, a significant reduction (p < 0.001) in MYC, CIS and PVAS expression was observed on D28. There was no significant difference in the percentage reduction of MYC, CIS and PVAS among the groups. Moreover, there was a significant difference (p < 0.05) in each group between D14 and D28, except for the percentage reduction in MYC in the 10FZ and 5IZ groups. No adverse effects of fluconazole were observed in the 5FZ or 10FZ groups.

CONCLUSIONS AND CLINICAL RELEVANCE

This study indicates that 5FZ and 10FZ are as effective as itraconazole in canine Malassezia dermatitis.

Oral fluconazole has variable pharmacokinetics in dogs

The purpose of this study was to assess the effects of food and manufacturer on the oral bioavailability of fluconazole in dogs. We hypothesized feeding would decrease fluconazole bioavailability and large variability between manufacturers would occur. Six healthy purpose-bred dogs aged 2-3 years, weighing 9.5-13.7 kg, were enrolled. Each dog was administered a 100 mg fluconazole tablet from three FDA approved manufacturers (1-Glenmark, 2-Citron, 3-Harris) in a randomized crossover block study, fasted for 12 h (fasted) or 15 min after feeding (fed); each dog had 6 treatments. Blood was collected for 72 h after dosing with a 10-day washout between treatments. Fluconazole plasma concentrations were determined with mass spectrometry. Overall variability in dose-normalized drug exposure (AUC/dose) was large (range 1.9-2.9x) within each treatment, while the overall range across all treatments was 3.3-fold. The inter-dog variability in the terminal half-life was also large, 3.1-fold. The mean fed relative oral bioavailability was lower (82%-90%) compared to fasted for each formulation. Due to the large variability, the formulations were not bioequivalent. These data suggest the variability in the half-life was a major contributor to the large variability in fluconazole pharmacokinetics in dogs, while the feeding status and manufacturer were minor contributors.