Antifungals Flashcards
What are the three types of antifungals?
1) Those against dermatophytes (like ring worm)
2) Those against yeasts
3) Those against systemic mycoses.
Dermatophytes can be treated both topically and systemically. T/F
True
What are some topical treatments for dermatophytes?
Lime-sulfur, azoles, thiabendazole, chlorhexadine, and iodine.
What are some systemic treatments for dermatophytes used for?
Onychomycosis (fungal nail infections), multifocal lesions, and in animals were topical treatment is impractical.
How does Griseofulvin work?
Disrupts the mitotic spindle microtubular structure, arresting metaphase. Effective ONLY on dermatophytes.
GIven orally, and absorption is increased if given with a fatty meal.
2 types: microsized and ultra-microsized.
What are some adverse reactions to Griseofulvin?
Hematologic - bone marrow supression.
GI upset
Teratogen - NEVER give to pregnant animals.
For how long do we treat with Griseofulvin?
3-4 weeks, but sometimes up to 12.
Onychomycosis treatment could be as long as 4-6 months.
Public health concerns with Griseofulvin?
Not to be administered to food animals.
What azoles can be used as systemic treatments for dermatophytes?
Terbinafine and Lufenuron.
Lufenuron is a flea treatment, but can be used as a preventative for fungi.
What routes of administration can be used for yeast therapy?
Topically, orally, or vaginally.
What is the site of action for Fluorocytosine (5-FC)?
Inhibits DNA and RNA synthesis via conversion of 5-fluorocytosine to 5-fluorouracil.
How is 5-FC eliminated?
Renal
What is 5-FC mainly used for?
Cryptoococcal meningitis in cats.
What are some adverse effects of 5-FC?
Bone marrow suppression
GI side effects
Hepatic toxicity.
What is the site of action for Amphotericin B?
Interrupts sterol synthesis in the cell membrane, resulting in leakage. Not very good for CNS infections.
Is Amphotericin B fungicidal or fungistatic?
Fungicidal!
Aspergilus is commonly resistant against Amphotericin B. T/F
True!
What route of administration is used for Amphotericin B?
IV ONLY
What are some adverse effects of Amphotericin B?
Cumulative nephrotoxicity via intense vasoconstriction leading to ischemic injury.
How is Amphotericin B eliminated?
Hepatic
What are the other formulations of Amphotericin B and what is their benefit?
Lipid-based and decrease kidney damage.
What is the site of action for azoles?
Azoles impair the synthesis of ergosterol (like Amphotericin B).
Are azoles fungicidal or fungistatic?
Fungistatic.
Ketoconazole:
Oral administration ONLY
Poor CNS penetration
Slow onset of action.
RARE hepatotoxicity. Primary side effects are GI related.
Inhibits testosterone and cortisol production.
Itraconazole:
Orally or IV admin, but oral is better.
Absoprtion enhanced by food and low gastric pH.
More rapid onset than ketoconazole.
Better penetration but still subtherapeutic in the CNS.
Fluconazole:
IV and orally.
Similar to Itraconazole in regards to onset.
WIDE tissue distribution - will enter urine, eye, and CNS.
Posaconazole:
Oral absorption enhanced by food.
Expensive, so limited use in vet med.
Voriconazole:
Active against aspergillus.
IV or oral admin.
Distributes throughout CNS, urine, and in the eye.
Fatty diet may decrease absorption, unlike other azoles.
Iodides are the most effective antifungal. T/F
False. Iodides are one of the lease effective antifungals, but they have many other uses. Only sporotrichosis is responsive to iodide therapy.
