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Block 6 Week 5 > Fungal Chemotherapy > Flashcards

Fungal Chemotherapy Flashcards

1
Q

What is selective toxicity?

A

your selectivey targeting particular pathways, enzymes, proteins, cell walls that are specific to the pathogen and not found in normal cells so that only the bad stuff is harmed

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2
Q

What is the cell size of a prokaryotic bacteria?

Eukaryotic fungi?

A

1-5 U to the third power

20-50 u to the third power

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3
Q

What is the ribsome type found in prokaryotes (bacteria)?

Eukaryotes (fungi)?

A

70S

80S

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4
Q

What is found in the cell wall of bacteria?

Fungi?

A

peptidoglycan

chitin

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5
Q

What is found in the membrane of bacteria?

fungi?

A

no sterols

ergosterols

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6
Q 
What kind of pathogens are these:
candida albicans
cryptococcus neoformans
pneumocystic jiroveci (carinii)
aspergillus
A

opportunistic pathogens-> systemic infections

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7
Q 
What kind of pathogens are these:
mucor
blastomyces dermatitidis
paracoccidiodes brasiliensis
histoplasma capsulatum
A

systemic infections

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8
Q

What are these:
epidermopyton
trichophyton
microsporum

A

superficial infections-dermatophytes

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9
Q

What are the drugs used for systemic infections?

A

polyene antibiotics
imidazole and triazole drugs
flucytosine
pentamidine

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10
Q

What are the drugs used for superficial infections?

A

polyenes
Azoles
Griseofulvin
naftifine

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11
Q

How does amphotericin B work?

A

disrupts the membrane

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12
Q

How should amphotericin B be given?

A

IV (mainly), topical, parenteral

NOT ORALLY

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13
Q

How should candicidin be given?

A

topically

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14
Q

How nystatin be given?

A

topically, orally for GI tract only

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15
Q

How should natamycin be given?

A

topically

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16
Q

What drug WILL be on the exam?

A

amphotericin B (KNOW THIS)

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17
Q

What kind of molecule is a polyene antibiotic?

A

large, lipophilic, water insoluble molecule

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18
Q

How do polyene antibiotics work?

A

they dissolve into cell membrane of fungi, bind to ergosterol in the membrane and increase the permeability to ions and metabolites

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19
Q

What is the selectivity of polyenes?

A

polyenes are toxic to fungi, protozoa and some algae. Selectivity is poor because human cell membranes also contain sterols (cholesterol). These drugs can be toxic :(

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20
Q

What do polyenes bind to?

A

sterols (selectivity is poor)

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21
Q

What are the polyene antibiotics?

A

Amphotericin B
Nystatin
Natamycin
Candicidin

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22
Q

What do you use amphotericin B for?

A

systemic fungal infections

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23
Q

What do you use nystatin?

A

topical treatment of skin, oral and intestinal Candida infections

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24
Q

What is used as a 5% opthalmic suspension?

A

natamycin

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25
Q

What do you use candicidin for?

A

topica treatment of vaginal candidiasis

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26
Q

What are the adverse reactions of polyene antibiotics?

A

FEVER, GI distress, cardiotoxicity, hemolytic anemia, leukopenia, hepatotoxicity, NEPHROTOXICITY

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27
Q

What are the adverse effects following IV infusion of amphotericin B?

A 
Fever
Chills
Hypotension
Vomiting
Dyspnea
Thrombophlebitis at injection site
Renal toxicity is invariable, but treatment can be continued to a creatinine concentration of 200mmol/liter
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28
Q

How can you attenuate the adverse effects of IV amphotericin B infusion?

A

with a slow infusion rate or by premedication with anti-histamines, antipyretics, meperidine or glucocorticoids

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29
Q

What 2 drugs are usually applied topically?

A

nystatin and candicidin

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30
Q

When can amphotericin B be given orally? When do you give it via IV?

A

for intestinal candida infection

for systemic infections

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31
Q

How do you eliminate polyene antibiotics? Does renal insufficiency affect half life significantly?

A

via kidney

no because the drug binds avidly to plasma membranes and slowly elutes into the blood stream. Elimination is very slow

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32
Q

(blank) is the drug of choice in most systemic fungal infections including systemic candidiasis. These infections are rare but quite dangerous. It can also be used in ointments for topical infections.

A

Amphotericin B

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33
Q

(blank) is often applied topically, but is also available as an oral preparation for oral and intestinal Candida infections.

A

Nystatin

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34
Q

(blank) is used topically to treat vaginal candidiasis

A

candicidin

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35
Q

What drugs are not very selective and are quite toxic?

A

polyene ntibiotics

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36
Q

(blank) is usually the dose-limiting toxicity of polyene antiobiotics

A

Nephrotoxicity

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37
Q

What are the two major groups of antifungal azole drugs?

A

imidazole

triazole

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38
Q

What are the 3 kinds of imidazole antifungal?

A

miconazole
clotrimazole
ketoconazole

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39
Q

What is the first orally active azole antifungal drug?

A

ketoconazole

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40
Q

How does ketoconazole work?

A

Increases permeability of fungal cell membranes by inhibiting ergosterol synthesis.
Blocks synthesis of ergosterol by inhibitin 14 alpha demethylase, a cytochrome p450 enzyme system

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41
Q

Is ketoconazole orally effective? What is its half life?

A

yes

12 hr

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42
Q

Is ketoconazole more toxic and more effective than amphotericin?

A

no it is LESS TOXIC

LESS effective

43
Q

What is the clincal use of Ketoconozole?

A

alternative to amphotericin B for treating systemic and mucocutaneous fungal infections

44
Q

What are some adverse reactions of ketoconazole?

A

nausea
GI disress
pruritis
Potentially fatal Hepatic toxicity and gynecomastia

45
Q

When should you stop use of ketoconazole?

A

if hepatitis occurs

46
Q

Ketoconazole also inhibits human (blank) synthesis by inhibiting cytochrom p450 enzymse. This is why you can get gynecomastia in males, and menstrual irregularities in females and decreased plasma cortisol levels.

A

steroid

47
Q

Because ketoconazole decreases cortisol evels, ketoconazole has been used to treat (blank)

A

cushings disease

48
Q

High dose ketoconazole should be avoided in patients with what disease?

A

TB
histoplasmosis
paracoccidiodomycosis
AIDS

49
Q

How does miconazole work?

A

messes up cell membranes of fungi by inhibiting ergosterol synthesis by inhibiting 14 alpha demethylase, a cytochrome p450 enzyme system

50
Q

How should you give miconazole?

A

topicaly, NOT GIVEN ORALLY

51
Q

Will you find miconazole in your CSF or urine?

A

no

52
Q

What is the clincal use of miconazole?

A

used mostly as topicl treatment of dermatophyte infections and treatment of vaginal candidiasis

53
Q

What are the adverse reactions of miconazole?

A

skin irriation

via IV admin can cause thrombophlebitis, rash nausea, anorexia

54
Q

What is clotrimazole used for?

A

to treat a variety of cutaneous and vaginal infections

55
Q

What are some adverse effects of clotrimazole?

A

local irritation and rash, GI distress may occur if drug is swallowed during topical oral admin for oropharyngeal candidiasis

56
Q

How should you give econoazole?

A

topical administration

57
Q

Why would you rather use itraconazole than ketoconazole?

A

because it has fewer adverse effects than ketoconazole and a wider spectrum of action.

58
Q

How is Itraconazole administered?

A

systemically

59
Q

What do you use itraconazole for?

A

drug of choice for several systemic mycoses.

60
Q

What are the triazole antifungal drugs and why are they more awesome than the Imidazole antifungals?

A

Itraconazole and Fluconazole
because they are metabolized more slowly and have less effect on human sterol synthesis and fewer side effects.
**NOTE: traiazoles have replaced ketoconazole for treatment of systemic mycoses*

61
Q

How is Fluconazole administered?

A

systemically

62
Q

What do you use fluconazole for?

A

cryptococcal meningitis in HIV positive pt.

Caninda in immune competent nt.

63
Q

What is the most frequently prescribed antifungal drug?

Why?

A

fluconazole

because it has the least effect on host cytochrome P450 enzymes and best therapeutic index of all azole compounds

64
Q

What is a newer antifungal drug belongin to the Echinocandin family and is used for systemic candiasis and as a LAST RESORT for aspergillosis refractory to amphotericin?

A

caspofungin

65
Q

What is the mechanism of action of caspofungin?

A

inhibits syntehsis of beta 1-3 glucan which disrupts fungal cell wall structure and reduces viability

66
Q

What is variconazole?

A

a recently introduced dug that is more specific for fungal p450

67
Q

What are naftifine and terbinafines?

A

broad spectrum, fungicidals

68
Q

What are the MOAs of naftifine and terbinafines?

A

inhibit squalene epoxidase and causes buildup of intracellular squalene which decreases ergosterol synthesis

69
Q

How is naftifine administered?

A

topically

70
Q

How is terbinafine administered?

A

orally active

71
Q

What do you use naftifine and teribafine for?

A

dermatophytes (tinea cruris and tinea corporis) Candida

72
Q

What is an adverse effect of natifine and terbinafine?

A

local irritation

73
Q

What is the enzyme naftifine and terbinafine block?

A

squalene epoxidase

74
Q

What is the enzyme that fluconazole, ketoconzole, itraconazoe, and variconzole block?

A

cytochrome p450 dependent 14alpha-demethylase

75
Q

What is the mechanism of action of fluctyosine?

A

prodrug-> turned into 5 flurouracil by fungal cytosine deaminase which release toxic metabolites into host cell that block RNA and DNA synthesis through reduction in thymidylate synthetase

76
Q

What is the spectrium of flucytosine?

A

narrow

77
Q

When does resistance to flucytosine occur?

A

when the drug is used alone

78
Q

What is the prodrug form of flucytosine?

A

5-fluorocytosine

79
Q

What is the fungal enzyme that converts the prodrug flucytosine into the antimetabolite? and what is the antimetabolite?

A

cytosine deaminase

5-fluorouracil

80
Q

5-fluorouracil inhibits (blank)

A

RNA and DNA synthesis

81
Q

How should flucytosine be used?

A

in combo w/ amphotericin B to treat systemic Cryptococcus and candida infections

82
Q

What are the adverse reactions to flucytosine?

A

bone marrow depression leading to leukopenia, thombocytopenia, GI distress, reversible hepatotoxicity. (toxicity may be a result of metabolism of flucytosine by GI flora to 5-fluorouracil)

83
Q

How does Griseofulvin work?

A

drug is actively transported into sensitive cells where it binds tubulin WHICH prevents proper separation of chromosomes during mitosis and interferes with transport functions of microtubules.

84
Q

How come griseofulvin has good selective toxicity?

A

because the drug has lack of active transport into mammalian cells

85
Q

With griseofulvin, about (blank) percent of an oral dose of micronized drug is absorbed. How can you increase absorption?

A

50%

if taken with a fatty meal

86
Q

What is the only way to administer griseofulvin?

A

ORALLY

87
Q

Griseofulvin has a unique pattern of distribution. The drug binds to (blank) and reaches high concentrations in the the skin and hair

A

keratin

88
Q

Griseofulvin is metabolized to glucuronide by the (Blank) and excreted via the (blnk)

A

liver

kidney

89
Q

What is the clinical use of griseofulvin?

A

effective against common dermatophytes; trichophyton, epidermophyton, microsporum. These fungi cause Tinea (ringworm)

90
Q

What are the adverse reactions of griseofulvin?

A
  • relatively safe drug, incidience of side effect is low
  • temporary headache is common in intial few days of therapy
  • nervous system-mental confusion, fatigue, visual impairment
  • GI distress
91
Q

How does pentamidine work?

A

binds to kinetoplast DNA and inhibits mitochondrial DNA synthesis. Blocks polyamine biosynthesis, blocks topoisomerase II.

92
Q

What is the clinical use of pentamidine?

A
  • pneumocystis jiroveci (carinii) infection in patients allergic to trimethoprimsulfamethoxazole.
  • aeroslize for prophylaxis against pneumocystic pneumonia in AIDS patients
  • also effective against African trypanosomiasis and leishmaniasis
93
Q

What are naftifine and terbinafine (lamasil) classified as?

A

broad spectrum, fungicidal drugs classified as allylmines.

94
Q

What do allylamines inhibit?

A

squalene epoxidase which cause buildup of intracellular squalene concentrations and decreases ergosterol synthesis

95
Q

What are allyamines effective against?

A

dermatophyts and candida.

Indications include tinea cruris, tinea corporis, and onychomyosis.

96
Q

Is terbinafine fungicidal?

A

yes

97
Q

Is the onset of action for allylamines faster or slower than imidazoles?

A

faster

98
Q

What drugs are used for sytemic infections?

A

polyene antibiotics
imidazole and triazole drugs
flucytosine
pentamidine

99
Q

What drugs are used for superficial infections?

A

polyenes
azoles
griseofulvin
naftifine

100
Q

(blank) is a fatty acid that is effective against Epidermophyton, the cause of tinea pedis (athlete’s foot). The mechanism of antifungal action is not known.

A

undecylenic acid

101
Q

(blank) is a synthetic topical drug that is effective against superficial infections by dermatophytes. The mechanism of antifungal action is unknown

A

tolnaftate

102
Q

A 28-year-old woman presents to the office complaining of 2-days of itchy vaginal discharge. One week ago you saw and treated her for a urinary tract infection (UTI) with sulfamethox-azole and trimethoprim (SMX-TMP). She completed her medi-cation as ordered and developed the vaginal discharge shortly thereafter. She denies abdominal pain, and her dysuria has resolved. She is not currently taking any medications. On examination, she appears to be comfortable and has normal vital signs. Her general physical examination is normal. A pelvic examination reveals a thick, curd-like, white discharge in her vagina that is adherent to the vaginal sidewalls. There is no cervical discharge or cervical motion tenderness, and bimanual examination of the uterus and adnexa is normal.

What is the most likely cause of these symptoms?
How would you treat this infection?

A

candida albicans

Flucanozole or Candicidin

103
Q

A debilitated cancer patient has bone marrow that is just beginning to recover from previous chemotherapy. He is still receiving three antibiotics to treat a presumed (but never proven) bacterial infection. An alert first year resident notices several new small pustules: a properly stained specimen of the pus reveals a yeast infection. At the same time, a blood culture grows out Candida albicans. Just before going off duty, the resident orders a new drug to treat the fungemia. The patient receives the first dose I.V., and immediately develops shortness of breath, hives, hypotension, fever and shaking. You are called to see the patient.

What is a likely cause of the new symptoms?
What alternate drugs might work?
What new adverse reactions might occur?

A

AmB
Azoles or flucytosine BUT the best one would be you wouldnt want to use flucytosine because it can have a bone marrow depression as a side effect!
Probably want to do flucanozole (less bad effects than ketoconazole)

Block 6 Week 5 (10 decks)

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