Flashcards in Antifungals Deck (48):
What are the 2 forms of pathogenic fungi?
Filamentous fungi and yeast
What characterises yeast?
Divide by budding
What characterises filamentous fungi?
Elongated cells divided by cell walls. Divide by spores
Appear in yeast and filamentous form depending on environmental conditions
5 antifungal targets
What is the main component of fungal cell walls?
beta 1-3 glucan
What is cholesterol equivalent component in the cell membrane of fungi?
What is the function of ergosterol?
Regulation of membrane permeability
Describe the formation of ergosterol
Squalene>squalene epoxidase>lanosterol>lanosterol 14 alpha demethylase>ergosterol
beta 1-3 glucan is a large polymer of what?
What enzyme synthesises beta 1-3 glucan?
beta 1-3 glucan synthase
What are the 4 classes of antifungals?
Give 2 examples of polyenes
Amphotericine B, Nystatin (not used anymore)
How do polyenes work?
Form pores in ergosterol membrane resulting in loss of membrane integrity and leakage of K+
Give 3 of fungi that AmB treats
Adverse effects of amphotericin B
Nephrotoxicity- pores form in human cell membranes
How is amphotericin B administered for serios/systermic infections?
How do lipid-associated Amphotericin B antifungals work?
Combining AmB to lipids minimises its delivery to kidney cells and reduces nephrotoxicity
In what cases is nystatin used?
Superficial infections e.g. oral/vaginal candidiasis
Clear cut nodule with cavity in teh middle of it. Fungus sits in the lung and causes localised infection.
Example of allyamines
What is terbinafine used for?
Athlete's foot-tinea pedis
How to allyalanines work?
Inhibit ergosterol synthesis
Is terbinafine broad spectrum or narrow spectrum?
Adverse effects of terbinafine?
Liver toxicity (jaundice, hepatitis)
Examples of dermatophyte infections that terbinafine is used to treat
Superficial fungal infections e.g. tinea pedis
Systemic use e.g. scalp ringworm, onychomosis
How do azoles work?
Inhibit ergosterol synthesis (lanosterol 14 alpha demethylase inhibitors)
Are azoles broad or narrow spectrum antifungals?
What antifungal is not effective against aspergillus?
2 types of azoles
What is the difference, structurally, between imidazoles and triazoles
Imidazoles- 2 N atoms
Triazoles- 3 N atoms
Which is more toxic; imidazoles or triazoles?
Example of an imidazole and what it's used for
Clotrimazole, used for candidiasis
3 examples of triazoles
Adverse effects of azoles
Hepatotoxicity (mild liver enzyme abnormalitis or life threatening hepatitis)
Drug interactions; inhibit cytochrome p450 enzymes so conc. of drugs that are metabolised by this enzyme increase
What types of fungi is fluconazole effective against
What types of fungi is itraconazole/vcorconazole effective against
What types of fungi is pasaconazole/isavuconazole effective against
How do echinocondins work?
Inhibit beta 1-3 glucan synthase resulting in the construction of severely abnormal cell walls
Example of echinocondin
What types of fungi are echinocondins effective against?
Aspergillus and candida, misses certain moulds and cryptococcus
Are echinocondons used for systemic or superficial infections, and how are they administered?
Systemic infections, parenteral formulations only
An antifungal that is a synthetic analogue of cytosine
How does 5 fluorocytosine work?
Inhibits RNA/DNA synthesis of fungal cytosine permease- prevents entry of fungus into the cell
What is 5 fluorocytosine effective against?
Yeasts e.g. Candida and cyptococcus
Adverse effects of 5 fluorocytosine
bone marrow suppression
What is 5 flurocytosine used for clinically
Crytococcal meningitis (in combination with AmB)