Itrafungol contains itraconazole, a synthetic broad spectrum triazole antimycotic with a high activity against dermatophytes (Trichophyton spp, Microsporum spp.), yeasts (Candida spp., Malassezia spp.), various dimorphic fungi, zygomycetes and eumycetes (e.g. Aspergillus spp.).

The mode of action of itraconazole is based on its highly selective binding ability to fungal Cytochrome P-450 iso-enzymes. This inhibits the synthesis of ergosterol and affects membrane-bound enzyme function and membrane permeability. This effect is irreversible and causes structural degeneration.

Laboratory animals rapidly absorb orally administered itraconazole. It binds very extensively to plasma proteins (>99 %) and distributes to tissues. More than 30 metabolites are formed, from which hydroxy-itraconazole has an antifungal activity as the parent. Excretion is rapid and mainly via the faeces.

In cats a single oral dose of 5 mg/kg results in maximum plasma concentrations of on average 0.525 mg/l attained 2 hours after dosing. The AUC0-24 h is 5 mg.h/l. The half-life in plasma is about 12 hours. After repeated administration for one week at 5 mg/kg/day, the maximum plasma concentration is more than doubled. The AUC0-24 h is increased 3 times to 15 mg.h/l and the plasma half-life is also increased 3 times to 36 hours.

In the therapeutic treatment schedule, itraconazole is almost completely cleared from plasma after each wash-out. In contrast to what happens in other animals, hydroxyitraconazole remains near or below the quantification limit in plasma after a single dose of itraconazole at 5 mg/kg. Concentrations in cat’s hair vary; an increase occurs during treatment to a median value of 3.0 μg/g (mean 5.2 μg/g) at the end of the third dosing week and concentrations drop slowly to 1.5 μg/g (mean 1.9 μg/g) at 14 days after the end of treatment. Concentrations of hydroxy-itraconazole in hair are insignificant.

Bioavailability of the oral solution of itraconazole in humans is higher when administered in fasted conditions.