Antimicrobials: antifungals Flashcards Preview

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Flashcards in Antimicrobials: antifungals Deck (41):
1

What fungus is most frequently associated with oral lesions?

1. Candida albicans
[mucocutaneous mycoses, thrush, denture stomatitis]

2

Is candida albicans the 1st most common organism isolated from US blood cultures?

NO, 4TH
HARD TO TELL IF IT IS COMMENSAL COLONIZATION OR PATHOGEN/INFECTION

3

What are the 2 categories of anti fungal drugs?

a. oral and parenteral drugs for
systemic therapy of systemic
infections
b. topical drugs for local therapy, and
oral drugs (for local or systemic
therapy) of mucocutaneous infections

4

What type of anifungals bind to ergosterol ?

polyene antibiotics

5

What type of anifungals associates with polymerized microtubules?

griseofulvin

6

What type of antifungals block ergosterol synthesis? 2

1. Azoles- bind fungal cytochrome P450 enzyme lanosterol 14-alpha-demethylase
2. allylamine

7

What structure is found in amphotericin B and nystatin?

lactone ring--(macrolide) polyene antibiotics

8

What anti-fungal has the broadest spectrum of anti fungal activity? when is it drug of choice? fungicidal?

1. Amphotericin
2. most life threatening systemic fungal infections
3. yes but may be static depending on environment etc.

9

What causes amphotericin adverse effects?

binding cholesterols [much less than ergosterol, but it does happen]

10

When is resistance to amphotericin B found? Is it rare?

1. when ergosterol concentration is low (azole treatment etc.)
2. if ergosterol affinity for amphotericin B is reduced

YES BUT MAY BE OBSERVED WITH CANDIDA SPECIES OTHER THAN C. CLBICANS

11

Is amphotericin absorbed well?

No- oral administration is only topical for GI

Must be parenteral for systemic infections. Not soluble

12

How are amphotericin metabolites excreted

renal

13

T-F--broad distribution of deoxycholate formulation of amphotericin B is a significant factor in toxicity?

True

14

What adverse effect is almost always seen to some degree with IV?

nephrotoxicity- slower with IV infusion as opposed to allergic/immediate

15

What 3 types of drugs have bad interactions with amphotericin B?

1. digitalis
2. azoles
3. nephrotoxic agents [aminoglycosides and cyclosporine]

16

What is critical for patients with renal dysfunction or requiring long-term amphotericin B therapy?

Liposomal preparations

17

Can nystatin be used parenterally?

No- too toxic

No absorbed through membranes so can be used topically everywhere

18

What does nystatin taste like?

bitter and very unpleasant taste

19

Is griseofulvin static or cidal?

statis

20

T-F--griseofulvin induces various CYP isoforms?

True--> alters effectiveness of various drugs including warfarin and oral contraceptives

21

is flucytosine static or tidal? oral or parenteral?

1. static
2. oral

22

What converts flu cytosine to 5-FU? What does 5-FU inhibit?

1. cytosine deaminase
2. Nothing--> 5-FdUMP which competitively inhibits thymidylate synthetase

23

What do we use flu cytosine in combination with to yield a synergistic effect? what disease?

1. amphotericin B -
2. Cryptococcus meningitis and severe candida

24

How do we get resistance to flucytosine?

mutations in cytosine permease or
cytosine deaminase

25

With flucytosine is oral bioavailability good? CNS penetration? hepatic excretions?

1. 90%
2. good CNS penetration
3. Renal excretion

26

Are azoles static or tidal? Oral or parenteral?

1. Static
2. both

27

T-F--triazoles are much less specific for fungal CYPs than imidazoles? T-f--- numerous drug interactions overall for this class?

1. False- other way around
2. True

28

What class of azoles is ketoconazole, miconazole, clotrimazole? Which azole has the greatest propensity to inhibit mammalian CYPS?

1. Imidazoles
2. Ketoconazole- may cause symptomatic hepatitis that can be fatal and dose independent

29

Is micronazole often used systemically?

no- thrombophlebitis after IV

30

What drug class is itraconazole, fluconazole, voriconazole, posaconazole, efinazonazole?

Triazoles

31

Is itraconazole absorbed well in the GI?

Yes

32

What are 3 key resistance facts of fluconazole

1. intrinsic resistance to C. krusei
2. Common in C. glabrata
3. Not active against mols like aspergillus

33

T-F-- voriconazole is less potent in vitro against yeast and molds than itraconazole? Is vori oral biovailability high? Which CYP is largely effected?

1. False- more potent in vitro
2. yes
3. CYP3A4

34

Does posaconazole have good oral bioavailability? what is it largely effective against?

1. Yes
2. zygomycoses

35

Is efinaconazole safe?

YES!! mono therapy for fungal toenail infections

36

What anti fungal class has a terbinafine structure? are they cidal or static?

1. allyamines
2. cidal

37

T-F-- allylamines and griseofulvins have the same dermatophyte target?

True

38

Where does terbinafine accumulate?

in the skin, nails, and fatty tissues

39

Co administration of terbinafine with what doubles its clearance? decreases its clearance?

1. Rifampicin
2. cimetidine

40

T-F--besides skin and nail infections, terbinafine is used for unusual refractory yeast infections?

False- mold infections

41

WHAT IS the newest class of antifungals? what does it cause to the cell wall? oral or parenteral?

1. glucan synthesis inhibitors
2. osmotic shock and lysis
3. parenteral IV