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Block 6 - week 5 > Fungal Pharmacology - Burkin > Flashcards

Fungal Pharmacology - Burkin Flashcards

1
Q

What if selective toxicity?

A

The targeting of specific microbe structures or pathways by anti-microbials that are not present in humans.

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2
Q

Name the fungi that cause systemic infections.

A
  1. Candida albicans
  2. Cryptococcus neoformans
  3. Pneumocystis jirocevi (carinii)
  4. Aspergillus
  5. Mucor
  6. Blastomyces dermatitidis
  7. Paracoccidiodes brasiliensis
  8. Histoplasma capsulatum
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3
Q

Which fungi are opportunistic pathogens?

A
  1. Candida albicans
  2. Cryptococcus neoformans
  3. Pneumocystic jiroveci
  4. Aspergillus
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4
Q

Which fungi cause superficial infections?

A
  1. Dermatophytes

2. Candida albicans

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5
Q

Name the Dermatophytes that cause superficial infections.

A
  1. Epidermophyton
  2. Trichophyton
  3. Microsporum
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6
Q

What drugs are typically used for systemic infections?

A
  1. polyene antibiotics
  2. imidazole and triazole drugs
  3. flucytosine
  4. pentamidine
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7
Q

What drugs are typically used for superficial infections?

A
  1. polyenes, azoles
  2. griseofulvin
  3. naftifine
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8
Q

Name the Polyene Macrolide antibiotics.

A
  1. Amphotericin B - topical, IV, parenteral
  2. Candicidin - topical
  3. Nystatin - topical, oral for GI tract only
  4. Natamycin - topical
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9
Q

What is the MOA of the Polyene drugs?

A

These drugs form pores in fungal membranes. They interact with ergosterol within the membrane and form a pore that causes the dysregulation of the membrane and eventual cell death. At high concentration these drugs can interact with cholesterol and cause pore formation in human cells (selectivity is poor).

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10
Q

What is Amphotericin B used for?

A

systemic fungal infections

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11
Q

What is Nystatin used for?

A

topical treatment of skin, oral and intestinal Candida infections

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12
Q

What is Natamycin used for?

A

used as a 5% ophthalmic suspension to treat eye infections

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13
Q

What is Candicidin used for?

A

topical treatment of vaginal candidiasis

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14
Q

What are the adverse reactions of the Polyenes?

A
  1. Fever
  2. nephrotoxicity
  3. GI distress
  4. cardiotoxicity
  5. hemolytic anemia
  6. leukopenia
  7. hepatotoxicity
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15
Q

What is a specific adverse effect of Amphotericin B?

A

If AmB is given too fast by IV infusion it can cause - fever, chills, hypotension, vomiting, dyspnea, thrombophlebitis at injection site and possible renal toxicity.

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16
Q

If a pt is has had a previous reaction to IV Amphotericin B how can you avoid a new occurrence?

A
  1. slow infusion rate

2. premedication with anti-histamines, antipyretics, meperidine or glucocorticoids

17
Q

Describe 2 broad categories of Azole anti-fungal drugs.

A
  1. Imidazole - has Imidazole ring - example is Ketoconazole

2. Triazole - has Imidazole ring with 3 nitrogens instead of 2 - Example is Itraconazole

18
Q

What is ketoconazole used for?

A
  1. second line agent (due to toxicity)

2. systemic and mucocutaneous infections

19
Q

Describe some characteristics of Ketoconazole.

A
  1. first orally active anti fungal
  2. orally effective - long half life
  3. less toxic but less effective than AmB
20
Q

What is the MOA of ketoconazole?

A

It blocks the synthesis of ergosterol by inhibiting the fungal enzyme 14a demethylase - a cytochrome P450 enzyme system.

21
Q

What are the adverse effects of ketoconazole?

A
  1. hepatic toxicity - it can inhibit human cytochrome P450
  2. inhibition of steroid synthesis - via inhibition of cyt P450
  3. high dose should be avoided in patients with TB, histoplasmosis, paracoccidiodomycosis and AIDS
22
Q

What are some other Imidazole antifungals and their uses?

A
  1. Miconazole - topical treatment of dermatophyte infections and treatment of vaginal candidiasis
  2. Clotrimazole - topical treatment of cutaneous and vaginal infections
23
Q

What are the Triazole antifungals and their uses?

A
  1. Itraconazole - wide spectrum, fewer side effects than ketoconazole, drug of choice for some systemic infections
  2. Fluconazole - Cryptococcus in HIV pt’s, Candida
  3. Variconazole - recently introduced, is more specific for fungal P450
24
Q

Describe some characteristics of Naftifine and Terbinafine.

A
  1. broad spectrum
  2. Naftifine - used topically
  3. Terbinafine - orally active
  4. used to treat Candida, and dermatophytes like tine cruris and tinea corporis
  5. can cause local irritation
25
Q

What is the MOA of Naftifine and Terbinafine?

A

These drugs inhibit squalene epoxidase which leads to a buildup of intracellular squalene. This decreases ergosterol synthesis and the build-up is toxic to the cell.

26
Q

Describe Flucytosine.

A
  1. is a prodrug that must be activated to 5-fluorouracil in the fungi.
  2. the enzyme that activates is called cytosine deaminase and is specific to fungi
  3. the fungi tries to use the 5-flurouracil to make RNA and DNA but it cannot be used so it stops transcription and replication.
27
Q

What can happen if Flucytosine is used on its own?

A

The rate of resistance is high.

28
Q

What is Flycytosine used for?

A

Combined with AmB to treat systemic Cryptococcus and Candida infections.

29
Q

What are the adverse reactions to Flucytosine?

A
  1. bone marrow suppression - leukopenia and thrombocytopenia
  2. GI distress
  3. reversible hepatotoxicity
30
Q

What is Pentamidine used for?

A
  1. treatment of Pneumocystis jiroveci (carnii)

2. also effective against African trypanosomes

31
Q

What is the MOA of Pentamidine?

A

It binds to kinetoplast DNA and inhibits mitochondrial DNA syntehesis, blocks polyamine biosynthesis and blocks topoisomerase II.

32
Q

What is Griseofulvin used for?

A

Dermatophyte infection such as Trichophyton, epidermophyton and microsporum. It is good for hair and skin infection because it binds to keratin and can reach high concentration in keratinized cells in the skin and hair.

33
Q

What is the MOA of Griseofulvin?

A

It binds to microtubules and inhibits their use in normal cell trafficking and growth.

34
Q

What are the adverse reactions of Griseofulvin?

A
  1. temporary headache
  2. GI distress
  3. CNS- mental confusion, fatigue, visual impairment

Block 6 - week 5 (8 decks)

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