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Clinical Pathology > Antifungals > Flashcards

Antifungals Flashcards

1
Q

What are the 2 forms of pathogenic fungi?

A

Filamentous fungi and yeast

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2
Q

What characterises yeast?

A

Divide by budding

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3
Q

What characterises filamentous fungi?

A

Elongated cells divided by cell walls. Divide by spores

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4
Q

Dimorphic fungi

A

Appear in yeast and filamentous form depending on environmental conditions

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5
Q

5 antifungal targets

A 
cell wall
cell membrane
protein synthesis
DNA synthesis
Mitosis
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6
Q

What is the main component of fungal cell walls?

A

beta 1-3 glucan

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7
Q

What is cholesterol equivalent component in the cell membrane of fungi?

A

ergosterol

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8
Q

What is the function of ergosterol?

A

Regulation of membrane permeability

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9
Q

Describe the formation of ergosterol

A

Squalene>squalene epoxidase>lanosterol>lanosterol 14 alpha demethylase>ergosterol

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10
Q

beta 1-3 glucan is a large polymer of what?

A

UDP glucose

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11
Q

What enzyme synthesises beta 1-3 glucan?

A

beta 1-3 glucan synthase

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12
Q

What are the 4 classes of antifungals?

A

Polyenes
Allylamines
Azoles
Echinocondins

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13
Q

Give 2 examples of polyenes

A

Amphotericine B, Nystatin (not used anymore)

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14
Q

How do polyenes work?

A

Form pores in ergosterol membrane resulting in loss of membrane integrity and leakage of K+

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15
Q

Give 3 of fungi that AmB treats

A

Aspergillus
Candida
Crytococcus

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16
Q

Adverse effects of amphotericin B

A

allergic reactions

Nephrotoxicity- pores form in human cell membranes

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17
Q

How is amphotericin B administered for serios/systermic infections?

A

Parenterally

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18
Q

How do lipid-associated Amphotericin B antifungals work?

A

Combining AmB to lipids minimises its delivery to kidney cells and reduces nephrotoxicity

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19
Q

In what cases is nystatin used?

A

Superficial infections e.g. oral/vaginal candidiasis

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20
Q

Clear cut nodule with cavity in teh middle of it. Fungus sits in the lung and causes localised infection.

A

Pulmonary aspergillosis

21
Q

Example of allyamines

A

Terbinafine

22
Q

What is terbinafine used for?

A

Athlete’s foot-tinea pedis

23
Q

How to allyalanines work?

A

Inhibit ergosterol synthesis

24
Q

Is terbinafine broad spectrum or narrow spectrum?

A

Broad

25
Q

Adverse effects of terbinafine?

A

Liver toxicity (jaundice, hepatitis)

26
Q

Examples of dermatophyte infections that terbinafine is used to treat

A

Superficial fungal infections e.g. tinea pedis

Systemic use e.g. scalp ringworm, onychomosis

27
Q

How do azoles work?

A

Inhibit ergosterol synthesis (lanosterol 14 alpha demethylase inhibitors)

28
Q

Are azoles broad or narrow spectrum antifungals?

A

Broad

29
Q

What antifungal is not effective against aspergillus?

A

Fluconazole

30
Q

2 types of azoles

A

Imidazoles

Triazoles

31
Q

What is the difference, structurally, between imidazoles and triazoles

A

Imidazoles- 2 N atoms

Triazoles- 3 N atoms

32
Q

Which is more toxic; imidazoles or triazoles?

A

Imidazoles

33
Q

Example of an imidazole and what it’s used for

A

Clotrimazole, used for candidiasis

34
Q

3 examples of triazoles

A

fluconazole
itraconazole
voriconazole

35
Q

Adverse effects of azoles

A

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

36
Q

What types of fungi is fluconazole effective against

A

yeasts

37
Q

What types of fungi is itraconazole/vcorconazole effective against

A

yeasts

aspergillus

38
Q

What types of fungi is pasaconazole/isavuconazole effective against

A

yeasts
aspergillus
mucuraceous moulds

39
Q

How do echinocondins work?

A

Inhibit beta 1-3 glucan synthase resulting in the construction of severely abnormal cell walls

40
Q

Example of echinocondin

A

AnidulaFUNGIN

41
Q

What types of fungi are echinocondins effective against?

A

Aspergillus and candida, misses certain moulds and cryptococcus

42
Q

Are echinocondons used for systemic or superficial infections, and how are they administered?

A

Systemic infections, parenteral formulations only

43
Q

An antifungal that is a synthetic analogue of cytosine

A

5 fluorocytosine

44
Q

How does 5 fluorocytosine work?

A

Inhibits RNA/DNA synthesis of fungal cytosine permease- prevents entry of fungus into the cell

45
Q

What is 5 fluorocytosine effective against?

A

Yeasts e.g. Candida and cyptococcus

46
Q

Adverse effects of 5 fluorocytosine

A

bone marrow suppression

47
Q

What is 5 flurocytosine used for clinically

A

Crytococcal meningitis (in combination with AmB)

48
Q

What 3 antifungals require therapeutic drug monitoring (to minimize toxicity and maximise efficacy)

A

5 flurocytosine
Itraconazole
Voriconazole

Clinical Pathology (53 decks)

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