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Pharmacology Test #2 > Antifungal agents > Flashcards

Antifungal agents Flashcards

1
Q

What are fungi

A

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

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2
Q

dimorphic fungi

A

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

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3
Q

examples of dimorphic fungi

A 
sporotrichosis
coccidioidomycosis
paracoccidioidomycosis
chromoblastomycosis
blastomycosis
histoplasmosis
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4
Q

Cells of fungi that are pathogenic in humans are

A

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

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5
Q

Mycoses are generally not transmissible except for

A

ringworm

thrush in newborn from candida albicans during childbirth

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6
Q

Dermatomycoses

A

filamentous fungi that live on keratinized tissue

itching, burning and cracking of skin

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7
Q

Onychomycoses

A

localized fungal infection of nail or nail bed

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8
Q

Examples of systemic infections by yeast-like fungi

A

histoplasmosis and candidiasis

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9
Q

Drugs used to treat dermatomycoses

A
  1. Tolnaftate
  2. Clotrimazole
  3. Griseofulvin
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10
Q

MOA of tolnaftate

A

inhibits fungal squalene epoxidase, resulting in decreased ergosterol biosynthesis

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11
Q

What is ergosterol?

A

the steroid present in fungal cell membranes

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12
Q

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

A

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

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13
Q

Other squalene epoxidase inhibitors used as antifungal agents

A

terbinafine
naftifine
butenafine

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14
Q

The azole class of antifungals inhibit

A

cytochrome P450

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15
Q

cytochrome P450 catalyzes

A

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

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16
Q

What does clotrimazole inhibit

A

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

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17
Q

Describe the selectivity of clotrimazole to human cytochrome P450

A

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

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18
Q

Other examples of azole antifungal agents

A

miconazole and ketoconazole

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19
Q

How does Griseofulvin work?

A

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

20
Q

What is griseofulvin used to treat?

A

used in the treatment of onychomycosis

deposited in newly formed keratin, where it prevents fungal growth

21
Q

What kind of diet can increase the absorption of griseofulvin?

A

high fat diet

22
Q

Adverse effects of griseofulvin?

A

photosensitivity, hypersensitivity and headache

23
Q

Antifungals to treat systemic infections

A
  1. Amphotericin B
  2. 5-Fluorocystosine
  3. Ketoconazole
  4. Fluconazole
  5. Itraconazole
  6. Echinocandins
24
Q

Describe the structure of Amphotericin B

A

amphoteric

lipophilic polyene region and a hydrophilic polyalcohol region

25
Q

Side effects of amphotericin B

A

fever and chills

sometimes headache, nausea, vomiting, nephrotoxicity and hypotension

26
Q

Major limiting toxicities of amphotericin B

A

nephrotoxicity and hypokalemia

27
Q

drug of choice for life threatening fungal infections

A

Amphotericin B

28
Q

Amphotericin B used to treat

A

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

29
Q

MOA of amphotericin B

A

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

30
Q

MOA of 5-fluorocytosine

A

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

31
Q

What does 5-fluorodeoxyuridine monophosphate inhibit

A

thymidylate synthase - thus inhibiting DNA biosynthesis

32
Q

5-fluorouracil incorporation into RNA in place of uracil does what

A

leads to the inhibition of protein synthesis

33
Q

5-fluorouracil functions as a

A

antimetabolite (analog of an essential substrate that is accepted by the metabolic pathway but cannot itself support the life of the cell)

34
Q

5-fluorocytosine (flucytosine) is used to treat?

A

used in combination with amphotericin B to treat systemic Candida infections and Cryptococcus neoformans meningitis

35
Q

Spectrum of activity for 5-fluorocytosine

A

limited to susceptible strains of Candida, Cryptococcus, Torulopsis glabrata, Cladosporium and Aspergillus

36
Q

Toxicity of 5-fluorocytosine

A

depresses bone marrow funciton (leukopenia and thrombocytopenia)
monitor kidney function
nausea, vomiting, diarrhea, rash and enterocolitis

37
Q

Ketoconazole used for

A

oral treatment of systemic infections

tolerated better than AmpB but less effective

38
Q

Ketaconazole treats

A

blastomycosis, histoplasmosis, coccidioidomycosis and paracoccidioidomycosis

39
Q

fluconazole used to treat

A

IV infusion to treat cryptococcal meningitis in AIDS patients
prevention of relapse of cryptococcal meningitis in AIDS patients
oral dose for treatment of vaginal candidiasis

40
Q

Toxicity of fluconazole

A

rare cases of hepatotoxicity

41
Q

Therapeutic uses of itraconazole

A

preferred treatment over ketoconazole for the treatment of nonmeningeal histoplasmosis (does not penetrate CSF)
AIDS patients with disseminated histoplasmosis

42
Q

Serious side effects of itraconazole

A

heart failure

rare severe hepatotoxicity

43
Q

coadministration of itraconazole is contraindicated with

A

cisapride, pimozide, quinidine and dofetilide

44
Q

Echinocandins inhibit

A

1,3-beta-glucan synthesis in the fungal cell walls by noncompetitive inhibition of 1,3-beta-glucan synthase

45
Q

Describe use of echinocandins

A

broad spectrum antifungal agents that have no cross-resistance with other antifungals and are synergistic with voriconazole and amphotericine B

46
Q

Adverse reactions of echinocandins

A

hepatotoxicity and sensitivity/allergic reactions

Pharmacology Test #2 (13 decks)

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