Veterinary Medicine - January 2008 - (Page 41)

PEER-RE VI E WED CE A review of selected systemic antifungal drugs for use in dogs and cats This pharmacologist reviews a few of your antifungal choices, speciﬁcally the azoles and terbinaﬁne. These drugs have a broad spectrum of activity—with some important differences. Butch KuKanich, DVM, PhD, DACVCP A lthough griseofulvin is the only antifungal approved for systemic administration by the Food and Drug Administration (FDA) for veterinary use, a variety of systemic antifungals are available for use in veterinary medicine. With the introduction of generic formulations, prescribing many of them is no longer cost-prohibitive. The development of newer antifungals such as itraconazole, uconazole, voriconazole, and posaconazole has been spurred on by the occurrence of resistance in fungal organisms, as seen in bacteria. This review addresses the mechanisms of action, potential indications, pharmacokinetics, adverse effects, and recommendations for the use of several azole antifungal drugs—ketoconazole, itraconazole, uconazole, voriconazole, and posaconazole—as well as terbina ne in veterinary patients. The azole antifungal drugs were rst discovered in the early 1970s, with ketoconazole being the rst orally active azole antifungal.1 The azoles have a broad spectrum of antifungal activity, but important differences exist. Terbina ne is not an azole antifungal drug, but it has a broad spectrum of activity against Butch KuKanich, DVM, PhD, DACVCP Department of Anatomy and Physiology College of Veterinary Medicine Kansas State University Manhattan, KS 66506 many yeast and fungal organisms. See Table 1 for the recommended dosages for these antifungals. MECHANISM OF ACTION The azole antifungal drugs have a similar mechanism of action, which is inhibiting the cytochrome P (CYP)-450dependent enzyme, lanosterol-14alphademethylase. This enzyme is responsible for forming ergosterol. Ergosterol depletion results in disruption of cell wall function. Lanosterol-14alpha-demethylase is present in most species of yeasts and molds with the exception of Pythium species.2 Lanosterol-14alpha-demethylase is also present in Leishmania species, which explains the variable activity of the azoles in leishmaniasis.3-5 The azoles have a higher af nity for fungal CYP A scanning electron photomicrograph of Cryptococcus neoformans (magniﬁcation X1,200). Image copyright Dennis Kunkel Microscopy, Inc. VETERINARY MEDICINE January 2008 41

Table of Contents Feed for the Digital Edition of Veterinary Medicine - January 2008

Veterinary Medicine - January 2008 Contents Digital Extra Letters Toxicology Brief Idea Exchange A Challenging Case: Phimosis in a Young Adult Dog The Indications and Technique for Continuous Ambulatory Electrocardiographic Recording in Dogs A Review of Selected Systemic Antifungal Drugs for Use in Dogs and Cats CE Form Advertiser Index Marketplace/Classifieds Mind Over Miller

Veterinary Medicine - January 2008

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