Antimyotics Flashcards
What are the 2 categories fungal disease falls under?
- dermatophytes
- internal disease
What fungus causes guttoral pouch mycosis?
aspergillus spp
What action do most antimycotic drugs have?
Fungistatic
What is the TI of most antifungals?
Low so side effects at higher conc
What are the 4 main antimycotics? (that effect the cell wall)
- polyenes
- azoles
- terbinafine
- echinocandins
What is the cholesterol equivelent in fungal cells?
Ergosterol
What is amphotericin B and what produces it?
Polyene proudced by some bacteria
What does amphotericicn B attach to?
ergosterol
Action of Amphotericin B
- forms pore in membrane
- internal acidification
- leakage of cell constituents
Is amphotericin B fungicidal or fungistatic?
fungistatic at concs usually used but -cidal at higher concentrations
What spectrum is ampotericin B?
Borad
How is amphotericin B given
IV
What limits the use of AB?
nephrotoxicity
(also GI disturbances, type I hypersensitivity)
What class of drugs does terbinafine belong to?
allylamin
What part of fungal cell wall synthesis does terbinafine inhibit?
squalene epoxidase
What can Terbinafine be used to treat?
(in dogs and cats)
dermatophytosis, subcutaneous and systemic fungal infections
What is the most common antimycotic?
Azoles
What do azoles inhibit?
C14a-demethylase
(a cytochrome p450 enzyme)
What is the action of azoles?
- inhibits synthesis of ergosterol, leads to accumulation of precursors
- disrupts membrane-bound enzyme activity
- inhibits cell growth
How are azoles administered?
orally
(also available as topical and IV formulations)
What is the Spectrum of azoles
- broad
- against skin or systemic infections
What is azole toxicity like ?
- relatively non toxic
- can cause nausea, vomiting, liver toxicity
How can fungal resistance occur in azoles?
- mutations in lanosterol 14alpha demethylase
- increased expression of lanosterol 14alpha demethylase
- expression of an azole efflux pump
What do echinocandins inhibit?
1,3-beta glucan synthase
What is the Echinocandin mechanism?
- reduce glucan synthesis
- glucans help maintain cell wall structure
- cell loses integrity and lyses
What are echinocandins useful for and an example of one?
- treating systemic aspergillosis and otehr fungal infections
- Capsofungin
What is Flucytosine
nucleoside analog, inhibits DNA and RNA synth
What is Griseofulvin
binds to microtubules and inhibits mitosis and cell growt
