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Flashcards in Antifungal agents Deck (46)
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1

What are fungi

eukaryotic organisms growing as single cells (yeasts) or as filamentous multicellular aggregates (molds)

2

dimorphic fungi

can grow as yeasts (oval or round) in host and molds (hyphae) at room temperature in vitro

3

examples of dimorphic fungi

sporotrichosis
coccidioidomycosis
paracoccidioidomycosis
chromoblastomycosis
blastomycosis
histoplasmosis

4

Cells of fungi that are pathogenic in humans are

nonmotile and have a rigid cell wall, usually containing chitin and polysaccharides

5

Mycoses are generally not transmissible except for

ringworm
thrush in newborn from candida albicans during childbirth

6

Dermatomycoses

filamentous fungi that live on keratinized tissue
itching, burning and cracking of skin

7

Onychomycoses

localized fungal infection of nail or nail bed

8

Examples of systemic infections by yeast-like fungi

histoplasmosis and candidiasis

9

Drugs used to treat dermatomycoses

1. Tolnaftate
2. Clotrimazole
3. Griseofulvin

10

MOA of tolnaftate

inhibits fungal squalene epoxidase, resulting in decreased ergosterol biosynthesis

11

What is ergosterol?

the steroid present in fungal cell membranes

12

Why is inhibition of ergosterol biosynthesis not cytotoxic to the host?

mammalian cells contain cholesterol in the cell membranes not ergosterol and fungal squalene epoxidase is more sensitive to tolnaftate than mammalian squalene epoxidase

13

Other squalene epoxidase inhibitors used as antifungal agents

terbinafine
naftifine
butenafine

14

The azole class of antifungals inhibit

cytochrome P450

15

cytochrome P450 catalyzes

the 14a-demethylation of lanosterol during its conversion to ergosterol

16

What does clotrimazole inhibit

the binding and activation of molecular oxygen by cytochrome P450 and therefore inhibits the conversion of lanosterol to ergosterol

17

Describe the selectivity of clotrimazole to human cytochrome P450

azoles have a greater affinity for the fungal cytochrome P450 than the human one, but the azoles still do bind to human cytochrome P450 and can inhibit drug metabolism

18

Other examples of azole antifungal agents

miconazole and ketoconazole

19

How does Griseofulvin work?

disrupts the mitotic spindle by binding to polymerized microtubles to inhibit mitosis

20

What is griseofulvin used to treat?

used in the treatment of onychomycosis
deposited in newly formed keratin, where it prevents fungal growth

21

What kind of diet can increase the absorption of griseofulvin?

high fat diet

22

Adverse effects of griseofulvin?

photosensitivity, hypersensitivity and headache

23

Antifungals to treat systemic infections

1. Amphotericin B
2. 5-Fluorocystosine
3. Ketoconazole
4. Fluconazole
5. Itraconazole
6. Echinocandins

24

Describe the structure of Amphotericin B

amphoteric
lipophilic polyene region and a hydrophilic polyalcohol region

25

Side effects of amphotericin B

fever and chills
sometimes headache, nausea, vomiting, nephrotoxicity and hypotension

26

Major limiting toxicities of amphotericin B

nephrotoxicity and hypokalemia

27

drug of choice for life threatening fungal infections

Amphotericin B

28

Amphotericin B used to treat

deep mycoses including aspergillosis, blastomycosis, coccidioidomycosis, cryptococcosis, histoplasmosis and mucormycosis

29

MOA of amphotericin B

binds to ergosterol in membranes of sensitive fungi, opening pores and allowing leakage of ions and small organic molecules

30

MOA of 5-fluorocytosine

susceptible fungi convert 5-fluorocytosine to 5-fluorouracil, which is converted into 5-fluorodeoxyuridine monophosphate