PHARMACOLOGY - Antifungal Drugs Flashcards
Why are fungal infections increasing?
Antibiotics disrupt the host microbiome allowing fungi to infect as fungi are resistant to antibiotics. The increased use of immunosuppressive drugs has also predisposed animals to fungal infections
Define fungicidal anti-fungal drugs
Fungicidal drugs kill fungi
Define fungistatic anti-fungal drugs
Fungistatic drugs inhibit fungal growth
What are the six main classes of anti-fungals use in veterinary medicine?
Allylamines
Azoles
Polyenes
Echinocandins
Antimetabolites
Griseofulvin
What is the mechanism of action for the allylamine anti-fungals?
Allylamines inhibit ergosterol biosynthesis through the inhibition of the squalene epoxidase enzyme
What is the spectrum of activity for allylamines?
Dermatophytes
How should allylamines be administered?
Oral
Topical
Why do allylamines persist within the skin when administered topically?
Allylamines are highly lipophilic so persist well in the skin
Lipophilic (dissolves in lipid)
Give an example of an allylamine
Terbinafine
What is the mechanism of action for azole anti-fungal drugs?
Azoles inhibit ergosterol biosynthesis through the inhibition of the 1,4 sterol-methylase enzyme
What is the spectrum of activity for azoles?
Broad spectrum
How should most azoles be administered?
Topical
Which group of azoles is available for systemic use?
Triazoles
Give a specific example of a triazole
Flucanozole
How should systemic azoles such as the triazoles be administered?
Intravenous (IV)
Oral
What are the three main mechanisms of resistance to azole anti-fungal drugs?
Mutation of the 1,4 sterol-methylase enzyme
Drug efflux
Biofilm formation
What is the mechanism of action for polyene anti-fungal drugs?
Polyenes bind to ergosterol and form pores in the fungal plasma membrane, disrupting the osmotic integrity of the cell causing the fungal cell to burst or undergo oxidative damage
What is the spectrum of activity for the polyenes?
Broad spectrum
How should polyenes be administered?
Intravenous (IV)
Topical
Give two examples of polyenes
Amphoterecin B
Nystatin
Why should nystatin only be administered topically and not intravenously (IV)?
Nystatin is toxic and can cause side affects such as nephrotoxicity, hypokalaemia and thrombophlebitis
Thrombophlebitis (inflammtion causing blood clots)
What is the mechanism of action for echinocandin anti-fungal drugs?
Echinocandins inhibit glucan synthesis through the inhibition of the beta 1,3 glucan synthase enzyme, causing the fungal cell wall to lose its structural integrity and undergo fungal cell lysis
What is the spectrum of activity for the echinocandins?
Candida
Aspergillus
How should echinocandins be administered?
Intravenous (IV)
