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Immuno mikro eng > Pharmacology of Antimicrobial Agents: Fungi and Antivirals > Flashcards

Pharmacology of Antimicrobial Agents: Fungi and Antivirals Flashcards

1
Q

What are the “endemic fungi”?

A

Histoplasmosis, blastomycosis, coccidiomycosis

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2
Q

Who is cryptococcus neoformans seen in? How is it tested for?

A

HIV patients with CNS infections

Tested for via rapid crpyto tests

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3
Q

What are the azoles?

A 
Flu-conazole
Itra-conazole
Vori-conazole
Posa-conazole
Isuva-conazole
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4
Q

What are the polyenes?

A

Amphotericin B

Nystatin

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5
Q

What are the Echinocandins? How do they differ?

A

Drugs ending in -fungin

They are all the same, just buy whichever is the cheapest

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6
Q

What are the miscellaneous antifungals?

A

Flucytosine
Griseofulvin
Terbinfine

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7
Q

What is one side effect we must always check for when using antifungals?

A

hepatotoxicity

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8
Q

What is the mechanism of action of azole antifungals and why is this clinically important?

A

Inhibits a Cytochrome P450 enzyme, inhibiting production of ergosterol, a component of the cell membrane

Important because it can interact with human CYP450 and cause drug interactions (slower metabolism, opposite of rifampin)

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9
Q

What are two Candida species which fluconazole is not reliable for and what should be used instead?

A

C. glabrata - use echinocandins instead

C. krusei - use voriconazole instead

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10
Q

What is the first line treatment for aspergillus? What azole is not active against it?

A

Voriconazole

Only fluconazole is not active against it

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11
Q

What are two side effects especially associated with voriconazole?

A

Nephrotoxicity and visual disturbances

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12
Q

What heart-related side effect do we worry about with azoles?

A

QT elongation, although isuvaconazole is a QT shortener

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13
Q

Which azole should be used for fungal UTIs and why?

A

Fluconazole, it is the only one renally dosed

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14
Q

Why is fluconazole typically relied on?

A

Only one with predictable absorption, all others require therapeutic drug monitoring

It is the empiric antifungal

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15
Q

What is the clinical application of itraconazole?

A

Non-life threatening cases of endemic mycoses

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16
Q

What are posaconazole / isuvaconazole used for?

A

Mucormycoses, with isuvaconazole’s niche to be determined

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17
Q

What is the mechanism of action of amphotericin B?

A

Binds ergosterol and forms pores in the membrane allowing molecules to leak in and out of the cell, causing cell death

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18
Q

What is amphotericin B the first line therapy for?

A 
Cryptococcus neoforms (serious CNS infection),
Endemic fungi when life-threatening (itraconazole otherwise), and mucormycoses (always serious)
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19
Q

What is amphotericin B’s Candida and aspergillus coverage?

A

Candida - broad coverage, including glabrata, but missing lusitaniae

Aspergillus - second line therapy due to safety (voriconazole is better)

20
Q

What are the side effects of amphotericin / amphoterrible B? How are these dealt with?

A
  1. Nephrotoxicity - causes holes in renal tubules leading to low K+ / Mg - consider Na+ loading to reduce AKI
  2. Infusion reactions - “shake and bake”, chills / rigors and fever. Premedication with tylenol / benadryl / steriods can decrease symptoms
21
Q

How was amphotericin B modified to be more tolerable?

A

Given in lipid formulation to try to clear it more via non-renal mechanisms (liver)

22
Q

How do echinocandins work?

A

Inhibit production of 1,3 beta glucan, a key component of many bacterial cell walls

23
Q

What organisms are echinocandins good against?

A

All candida species, considered first line for all, except maybe C. parapsilosis

Aspergillus - used in combination therapy if patient is intolerant to voriconazole or amphotericin

24
Q

How are echinocandins administered and why are they juicy as fork?

A

IV - juicy because they have little toxicity profile, but not renally cleared (no UTI)

25
Q

When would you know to use echinocandins vs fluconazole for yeast infection?

A

If patient is not critically ill and this is new, use fluconazole

If recent azole exposure, known colonizer with C. glabrata, or critically ill, use echinocandins

26
Q

What is the mechanism of action of flucytosine?

A

Converted into 5-fluorouracil by fungal cells, inhibiting DNA/RNA synthesis

27
Q

What antibiotics can flucytosine be equated to? When is it used?

A

Aminoglycosides -> not used as monotherapy outside of UTIs

Used with amphotericin B for severe infections, including candida endocarditis and Cryptococcus neoformans infections

28
Q

What are the side effects of flucytosine?

A

Dose-dependent bone marrow suppression

29
Q

What drugs work for fungal UTIs?

A

fluconazole, amphotericin, flucytosine

30
Q

What type of virus is CMV?

A

Betaherpesvirus, causes mononucleosis in myeloid line of cells, more serious in adulthood

31
Q

What is the mechanism of action of acyclovir?

A

Drug modified by viral thymidine kinase to become monophosphate derivative, then host enzymes convert to triphosphate. This acts as a chain terminator in growing DNA, competitively inhibiting viral DNA polymerase

32
Q

What is acyclovir used for?

A

HSV

varicella/zoster virus at higher doses

33
Q

Why is acyclovir rarely given orally? What is given instead?

A

Not well absorbed, requires 5x a day dosing

Instead: Valacyclovir, the oral prodrug of acyclovir which is well absorbed

34
Q

When would you want to give IV acyclovir vs oral valacyclovir?

A

When the infection is very serious

35
Q

What are the side effects of IV acyclovir?

A

headaches, crystallization in urine at high doses (not fully dissolved) so keep hydrated, neurotoxicity at high doses

36
Q

What is the mechanism of action of ganciclovir?

A

Same as acyclovir in HSV / VSV

In CMV: Activated by kinase phosphotransferase (Rather than thymidine kinase), then same steps

37
Q

What is ganciclovir used for? How is it given PO?

A

Used as drug of choice for CMV

Valganciclovir is used for less serious infections and is more orally available

38
Q

What is the major side effect associated with ganciclovir?

A

Bone marrow suppression -> VERY COMMON, bad since immunosuppressed need this
CNS effects -> headache to coma

39
Q

What is the mechanism of action of Cidofovir?

A

Cytosine nucleotide analog which does not require viral activation

40
Q

What is the spectrum for cidofovir and when is it used?

A

HSV, VZV, CMV

Used for CMV when CMV is resistant to ganciclovir / foscarnet

41
Q

What are the major side effects of cidofovir?

A

Nephrotoxicity / neutropenia

42
Q

What is the mechanism of action of foscarnet?

A

inorganic pyrophosphate compound, inhibits DNA polymerase, RNA polymerase, and HIV reverse transcriptase

43
Q

When is foscarnet used and what are its big side effects?

A

Only for CMV when ganciclovir is not available

Side effects: Nephrotoxicity, CNS effects, potential chelator of divalent cations in blood

44
Q

What do neuraminidase inhibitors do and when are they used?

A

Inhibits viral neuraminidase, in influenza A and B. Only used within 48 hours of symptom onset, otherwise all cells are infected anyway (static).

45
Q

What are the major neuraminidase inhibitors and what is one side effect?

A

Zanamivir (IV), oseltamivir (PO)

Zanamivir can exacerbate COPD if inhaled

46
Q

What are the antifungals for dermatophytes (tinea) and how do they work?

A

Terbinafine - blocks ergosterol production via inhibition of squalene epoxidase

Griseofulvin - blocks infection of new skin structures, eventually old infections get replaced

Immuno mikro eng (56 decks)

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