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A13AMC @ UoN > L12 - Treatment of Fungal Diseases > Flashcards

L12 - Treatment of Fungal Diseases Flashcards

1
Q

What are the four main classes of antifungals? - Give an example

A

Polyenes (Amphotericin B)
Azoles (Voriconazole)
Echinocandins (Caspofungin)
Allylamines (Terbinafine)

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2
Q

What is the MoA of Polyenes?

A

Polyenes bind to Ergosterol in the cell membrane, weakening it

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3
Q

What is the MoA of Azoles?

A

Azoles inhibit the conversion of Lanosterol to Ergosterol (c14a-demthylase)

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4
Q

What is the MoA of Allylamines?

A

Allylamines inhibit the conversion of Squalene to Lanosterol (Squalene epoxide)

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5
Q

What is the MoA of Echinocandins?

A

Echinocandins inhibit glucan synthesis in the cell wall (B-1,3-D-glucan synthase)

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6
Q

What is the MoA of 5-Flucytosine?

A

5-Flucytosine is an antimetabolite pyrimidine analogue

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7
Q

Define selective toxicity

A

The ability to be toxic to microbial cells but not host cells

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8
Q

What are the problems with selective toxicity?

A

Sterols (cholesterol) are present in host plasma membranes
CYP450 system in host hepatocytes
Nucleic acids in host cells

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9
Q

How can we achieve selective toxicity?

A

Topical application

Target specificity

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10
Q

Describe Amphotericin B toxicity - Acute reactions

A

30 mins post infusion
Chills, fever, SoB, drop in BP, aches
Peaks @ 1h, lasts <4h
Induction of Prostaglandin E2

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11
Q

How can we treat for Amphotericin B toxicity? - Acute reactions

A

Test doses and escalate slowly

Pre-medicate (NSAIDs/steroids)

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12
Q

Describe Amphotericin B toxicity - Renal toxicity

A

Vasoconstriction of afferent renal aa
K, Mg, HCO3- loss
Decreased EPO
Loss of nephrons

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13
Q

How can we treat for Amphotericin B toxicity? - Renal toxicity

A

Regular renal monitoring
Electrolyte replacement
Amiloride

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14
Q

Describe Amphotericin B toxicity - Rarer symptoms

A

Anorexia, nausea, vomiting
Phlebitis
Gradual anaemia (decreased EPO)
Thrombocytopaenia, leucopenia, coagulopathy
Tinnitus, vertigo, seizures, encephalopathy
Anaphylaxis/allergy

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15
Q

What is an appropriate dose of AmB?

A

3-5mg/kg

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16
Q

What are the three lipid formulations of Amphotericin B?

A

Liposomal AmB (L-AmB)
AmB colloidal dispersion (ABCD)
AmB lipid complexes (ABLC)

17
Q

Describe L-AmB

A

60-70nm vesicles

18
Q

Describe ABCD

A

~115nm diameter discs

19
Q

What is the disadvantage of lipid formulations of AmB?

A

Expense

20
Q

Why do we use lipid formulations of Amphotericin B?

A

AmB is released by preferential affinity to Ergosterol/action of phospholipase, avoiding toxicity

21
Q

Describe ABLC

A

1600-11000nm ribbons

22
Q

Describe the Antifungal spectrum

A

AmB - Largely effective (Scedosporium)
Fluc - Rarely effective
Itra - Somewhat effective
Vori - Largely effective

23
Q

How does resistance to AmB arise?

A

Alteration of Ergosterol (reduces fungal fitness)

24
Q

How does resistance to Azoles arise?

A

Altered c14a demthylase

Efflux mechanisms

25
Q

How does resistance to 5-Flucytosine arise?

A

Decreased permeability
Altered phosphorylation
Resistance only common in monotherapy

26
Q

Describe the formulation of Echinocadins

A

Lipopetide side chains determine solubility

i.v. route only

27
Q

What is the activity of Echinocandins restricted to?

A 
Candida spp (cidal)
Aspergillus spp (static)
28
Q

What are the side effects of Echinocandins?

A 
Phlebitis
Fever
Headache
Hepatotoxicity
Haemolysis
29
Q

Define mycoses

A

Mild to severe infections with fungi

30
Q

Give examples of the superficial mycoses

A

Skin - Dermatophytosis
Nails - Onychomycosis
Mucous Membranes - Candidasis

31
Q

Give examples of the deep mycoses

A

Invasive candidasis
Aspergillosis
Cryptococcosis

32
Q

What moulds cause dermatophytosis? - Tineas

A

Trichophyton
Microsporum
Epidermophyton

33
Q

What yeasts cause dematophytosis?

A

Malassezia

34
Q

What predisposes patients to invasive candidasis?

A

Indwelling devices
Damaged mucosae
Immunocompromised

35
Q

What antifungals are used to treat invasive candidasis?

A

AmB
Fluconazole
Caspofungin
Micafungin

36
Q

What antifungals are used to treat aspergillosis?

A

AmB
Itraconazole
Voriconazole
Caspofungin

37
Q

What problem does cryptococcus cause in HIV?

A

Meningitis

38
Q

What antifungals are used to treat cryptococcus?

A

AmB +/- 5-Flucytosine

39
Q

What antifungals are used to treat endemic mycoses?

A

AmB

Itraconazole

A13AMC @ UoN (20 decks)

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