484 DISEASES/DISORDERS
inhibitor of cytochrome p450 enzymes; avoid concurrent use with ivermectin – may
exacerbate ivermectin toxicity; contraindicated in cats due to impaired metabolism of
the drug; patients should be monitored with routine blood work for hepatotoxicity.Fluconazole: minimal side effects, safe option; moderate inhibitor cytochrome p450
enzymes.
Itraconazole: often well tolerated; specific for fungal cytochrome p450 enzymes;
mild inhibitor of mammalian cytochrome p450 enzymes; dose with food for best
absorption; concurrent use with oral antacids will decrease oral absorption; mon-
itor for hepatotoxicity; specific has little effect on hormone synthesis and will
not produce endocrine effects; adverse effects – vasculitis and ulcerative skin
lesions.Terbinafine: hepatotoxicity not reported from use in animals; facial pruritus has been
reported in cats; no contraindications or drug interactions; vomiting most common
side effect.COMMENTS
Facts for Pet Owners aboutMalassezia
FACT Normal commensal yeast organism on the surface of the skin.Malassezia pachyder-
matiscan be found on normal dogs primarily around the nose, ears, mouth, anus,
axillae, anal sacs, skin folds, claw folds, and interdigital regions. Often seen as a
red-brown discoloration at the base of the nails and interdigital webs. Yeasts love
moist, dark crevices. Humidity is yeast’s friend. Seborrheic skin and allergic skin
are prone to yeast overgrowth.FACT Yeasts create a rancid, pungent, musty odor (described as “corn chip” or “Frito-
feet”).
FACT Malasseziahas a symbiotic relationship with staphylococcal bacteria. More bacte-
ria on the skin=more yeast on the skin. Staphylococcal bacteria andMalassezia
yeast produce mutually beneficial growth factors and alterations in their microen-
vironment. It is common for dogs with a yeast overgrowth to also have a bacte-
rial folliculitis. Yeasts produce proteins and glycoproteins that allow staphylococcal
bacteria to adhere to skin cells. Yeast organisms do not invade the skin beyond the
outer layer (stratum corneum). Yeast “dermatitis” results from an inflammatory or
hypersensitivity reaction to yeast products and antigens.FACT Malassezia pachydermatisproduces a number of inflammatory products that cause
the skin to become moist, red, thickened with chronicity, and very itchy. These
products alter the skin’s pH and activate the inflammatory cascade in the skin that
results in a hypersensitivity reaction. Chronic exposure to these products causes
the skin to become thickened and lichenified (elephant skin). Constant scratching,
licking or rubbing of the skin will also contribute to skin thickening...it is the
“perfect storm.”
FACT intradermal skin testing for environmental allergies (trees, grasses, weeds, pollens,
molds, dust mites, etc.) can also identify an allergy to yeast.