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Pharmacology -- Test #2 > Anti-Fungals > Flashcards

Anti-Fungals Flashcards

1
Q

Two ways that fungi can grow

A 
Single Cell (Yeasts)
Filamentous Multicellular Aggregates (Molds)
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2
Q

Yeasts typically reproduce by…

A

budding

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3
Q

Molds are made of…

A

hyphae

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4
Q

What are dimorphic fungi?

A

Ones that can grow as either yeasts or molds

Yeast in host

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5
Q

Six important dimorphic fungi

A 
Sporotrichosis
Coccidiomycosis
Paracoccidiomycosis
Chromoblastomycosis
Blastomycosis
Histoplasmosis
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6
Q

How do fungi reproduce?

A

Forming spores through mitosis or forming sexual spores

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7
Q

Fungi growing sexual spores are said to be in…

A

the perfect state

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8
Q

Describe the cell wall of a pathogenic fungus

A

Nonmotile, Rigid

Contain Chitin and Polysaccharides

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9
Q

What mycoses are transmissible from person to person?

A

Scalp ringworm

Thrush in the newborn (from mom with Candida)

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10
Q

Important details for dermatomycoses.

A

Filamentous fungi on keratinized tissue (skin, hair, nails)
Symptoms - Itching, burning, crackling of skin
Examples - Athlete’s Foot, Ringworm, Jock Itch)

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11
Q

Important details for onychomycoses?

A

Localized fungal infection of the nail or nail bed
Caused by dermatophyte
Thickening of nail (white, yellow, or brown)

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12
Q

Two examples of yeast-like fungi involving internal organs

A

Histoplasmosis

Candidiasis

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13
Q

Anti-fungals for Dermatomycoses?

A

Tolnaftate (Tinactin)
Clotrimazole (Lotrimin)
Griseofulvin

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14
Q

Tolnaftate mechanism of action?

A

Inhibition of Fungal squalene epoxidase
Results in loss ergosterol synthesis in fungi
Loss of membrane stability

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15
Q

Why is tolnaftalate selective for the fungus and not the host?

A

Humans use cholesterol, not ergosterol

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16
Q

Three non-tolnaftate squalene epoxidase inhibitors?

A

Terbenafine
Naftifine
Butenafine

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17
Q

Clotrimazole is administered how?

A

Vaginal Tablet

Topical

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18
Q

Clotrimazole is a member of the _____ class of antifungal agents

A

Azole

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19
Q

What do azoles do against fungi?

A

Inhibit Cytochrome p450 (which catalyzes 14alpha demethylation of lanosterol in ergosterol production) by inhibiting the binding/activation of molecular oxygen

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20
Q

Selectivity of Azoles?

A

Greater affinity for fungal cytochrome p450 than human

Selectivity is not absolute

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21
Q

Non-Clotrimazole azoles listed?

A

Miconazole

Ketoconazole

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22
Q

Griseofulvin is used for…

A

Systemic treatment of dermatomycoses

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23
Q

How does Griseofulvin work?

A
  • It disrupts mitotic spindle binding to polymerized microtubules (inhibiting mitosis).
  • Binds in newly formed keratin to prevent fungal growth
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24
Q

Griseofulvin is used to treat..

A

Onychomycosis (fungal infections of the nails)

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25
Q

Why does Griseofulvin take so long?

A

Keratin in old tissues may still support fungal growth

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26
Q

Dissolution rate of Griseofulvin?

A

Very slow (because it is water insoluble)

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27
Q

How to improve the dissolution rate of Griseofulvin?

A

Microsize and ultramicrosize particles

Taken in a high fat diet

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28
Q

Adverse effects of Griseofulvin?

A

Photosensitivity, Hypersensitivity, Headache

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29
Q

Antifungals used to treat systemic infections?

A 
Amphotericin B
5-Fluorocytosince
Ketoconazole
Fluconazole
Itraconazole
Echinocandins
30
Q

Amphotericin B is amphoteric…what does that mean

A

Acidic and a Basic Group

31
Q

Specific phillicities of Amphotericin B?

A

Lipophillic polyene region (bottom)

Hydrophilic polyalcohol region

32
Q

Absorption info for Amphotericin B?

A

Poor water solubility
Not absorbed well in GI
Must be administered by slow IV infusion

33
Q

What is the Amphotericin B deoxycholate complex or cholesterol complex?

A

A bile salt complex which is reconstituted with sterile water
(you can also get it as a liposomal suspension for injection, but I don’t feel like making another card for it)

34
Q

Major acute rxns to Amphotericin B?

A

Fever and Chills

Sometimes HA, Nausea, Vomiting, nephrotoxicity, HTN

35
Q

Major limiting toxicities of Amphotericin B?

A

Nephrotoxicity

Hypokalemia

36
Q

Name six fungal infections that Amphotericin B is the drug of choice for?

A 
Aspergillosis
Blastomycosis
Coccidiomycosis
Cryptococcosis
Histoplasmosis
Mucormycosis
37
Q

Mechanism of action for Amphotericin B?

A

Binding to ergosterol in the membranes
Pores open in the membrane
Leakage of ions and Small organic molecules

38
Q

Selectivity of Amphotericin B?

A

Binds 10 times more strongly to vesicles containing ergosterol than those with cholesterol
BUT some cholesterol binding still occurs, resulting in toxicity

39
Q

Mechanism of 5-Fluorocytosine action?

A

Susceptible fungi convert 5-Fluorocytosine to 5-Fluorouracil, which is conversed to 5-fluorodeoxyuridine monophosphate

40
Q

5-fluorodeoxyuridine monophosphate inhibits…

A

Thymidylate synthase

An enzyme required for DNA synthesis

41
Q

Steps of Biosynthetic conversion of deoxyuridine monophosphate

A
  1. Michael addition to Uracil to make an enolate
  2. Added to iminium ion in methelene-THF
  3. Intermediate eliminates THF, forming uracil derivative
  4. In Michael addition, enolate is generated
  5. Enzyme is eliminated to generate final product
42
Q

How does the presence of 5-fluorouracil influence the deoxyuridine monophosphate mechanism?

A

Elimination of F+ is impossible
Nothing around to be more electronegative
Leaves a big-ole unbreakable chain

43
Q

Aside from problems with the generation of thymidylate synthase, what else does 5-fluorouracil do to prevent fungi?

A

It incorporates into RNA in place of uracil
Inhibited protein synthesis
5-fluorouracil = antimetabolite

44
Q

What is an anti-metabolite?

A

The analog o an essential substrate that is accepted by the metabolic pathway, but cannot itself support life in the cell

45
Q

5-Fluorocytosine selectivity?

A

Human cells have little or no cytosine deaminase activity

46
Q

Therapeutic use of 5-Fluorocytosine?

A

Used w/ Amp. B on systemic Candida+Cryptococcus meningitis.

Sometimes torpulopsis glabrata, cladosporidium, and aspergillis

47
Q

Resistance to 5-Fluorocytosine?

A

With with Amp. B to kill resistant strains

48
Q

How does 5-Fluorocytosine function change with Amph. B added?

A

Amph. B fucks up the fungal cell permeability

Makes it easier for 5-Fluorocytosine to get up in there

49
Q

Toxicity associated with 5-Fluorocytosine?

A

Depressed Bone Marrow Fxn - Leukopenia, thrombocytopenia
Nausea, Vomiting, Diarrhea
Rash, Entercolitis

50
Q

5-Fluorocytosine should be administered with extreme caution to which patients?

A

Bone marrow depression

Diminished renal function

51
Q

How might 5-Fluorocytosine nausea be diminished?

A

Capsules administered a few at a time over a 15 minute period

52
Q

Important details on Ketoconazole?

A

Oral treatment of systemic infection

Better tolerated than AmpB, but less effective

53
Q

What is Ketoconazole used to treat?

A

Bastomycosis
Histoplasmosis
Coccidiomycosis
Paracoccioiomycosis

54
Q

Describe the structure of Fluconazole?

A 
A triazole (3 Ns in a 5 membered ring)
Not an Imidazole (2Ns)
55
Q

Bioavailability of Fluconazole?

A

High bioavailability

Penetrates into the CSF

56
Q

Selectivity of Fluconazole?

A

Selective for Fluconazole cytochrome p450

57
Q

Therapeutic use of Fluconazole?

A

IV infusion – Cryptococcal memingitis in AIDS patients whose infection has been controlled by AB
Single dose – Vaginal candidiasis

58
Q

Toxicity assocaited with Fluconazole?

A

Rare cases of hepatotoxicity (including fatalities)

59
Q

Itraconazole is a mix of…

A

Four Diastereomers

60
Q

Itraconazole availability….

A

90% bound to serum proteins, extensively bound in tissues

61
Q

Can Itraconazole be used to treat CSF infections?

A

Nope

No detectable drug in the CSF

62
Q

Therapeutic use of Itraconazole?

A

Preferred over keto for non-meningeal histoplasmosis.

AIDS pateints w/ disseminated Histo (stabilized by AB)

63
Q

Untoward effects of Itraconazole?

A

GI distress (at 400mg/day or more), Nausea, Vomiting
Hypokalemia, Rash
Heart Failure
Hepatotoxicity

64
Q

Itraconazole cannot be coadministered with…

A

drugs metabolized by Cytochrome p450

ex. cisapride, pimozide, quinidine, dofetilide

65
Q

Functional activity of Echinocandins?

A

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

66
Q

Selectivity of Echinocandins?

A

Good because mammalisn cells lack 1,3 beta-glucan synthase

67
Q

Cross resistance of Echinocandins?

A

None

68
Q

Echinocandins are synergistic with…

A

Voriconazole and Amph. B

69
Q

Mode of administration for Echinocandins?

A

IV

70
Q

Adverse reactions to Echinocandins?

A

Hepatotoxicity

Sensitivity/Allergic Reactions

Pharmacology -- Test #2 (13 decks)

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