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Pharma 2nd semester > C.4. Antifungal agents > Flashcards

C.4. Antifungal agents Flashcards

1
Q

list 2 Polyenes

A

Amphotericin B and Nystatin

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2
Q

mechanism of action of Amphotericin B and Nystatin

A
  1. interact with ergosterol in fungal membranes to form ‘pores’, which disrupt membrane permeability
  2. Fungicidal effect
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3
Q

what is the basis of Amphotericin and Nystatin resistance?

A

strains that have low ergosterol content in their cell membranes are resistant

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4
Q

spectrum and clinical use of Amphotericin B

A

broadest antifungal spectrum.

systemic infections: Aspergillosis, Blastomyces, candida, Cryptococcus, Histoplasma, Mucor, Sporthrix

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5
Q

clinical use of Nystatin

A

topical for candidiasis

*systemic use is limited due to toxicity

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6
Q

how is Amphotericin given?

A

IV or orally (poor availability)

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7
Q

what is the T1/2 of Amphotericin B?

A

up to 2 weeks

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8
Q

does Amphotericin B have CNS penetration?

A

poor

an intrathecal injection is required against cryptococcal or candida meningitis

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9
Q

clearance of amphotericin

A

hepatic metabolism and renal elimination

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10
Q

adverse effects of Amphotericin infusion-related

A

fever, chills
muscle spasm
injection site phlebitis
hypotension (due to histamine release)

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11
Q

adverse effects of Amphotericin dose-dependent

A
  1. nephrotoxicity (↓ GFR, RTA, K and Mg² wasting, ↓EPO)
  2. CNS toxicity (seizures)
  3. Anemia
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12
Q

what are the means to reduce infusion-related toxicity with Amphotericin administration (4)?

A
  1. anti-histamines
  2. NSAID’s
  3. Meperidine- opioid
  4. Corticosteroids
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13
Q

what are the means to reduce dose-dependent toxicity with Amphotericin administration (4)?

A
  1. liposomal formulation of Amphotericin B
  2. Co-administration with flucytosine
  3. volume expansion with IV saline
  4. K and Mg² supplementation
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14
Q

mechanism of action of azoles

A
  1. interfere with the synthesis of ergosterol

2. Fungicidal effect

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15
Q

resistance mechanism of azoles

A

develops with long term use via ↓ intracellular accumulation and altered sensitivity of target enzymes

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16
Q

what are ketoconazole, clotrimazole and Miconazole?

A

Imidazoles

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17
Q

what is Fluconazole and Itraconazole?

A

1st generation Triazoles

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18
Q

what is Voriconazole?

A

2nd generation Triazole

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19
Q

how are azoles given?

A

oral, parenteral, topical

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20
Q

which azole can penetrate the CSF and cross the BBB?

A

fluconazole

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21
Q

are azoles inhibitors of CYP450 enzymes?

A

yes

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22
Q

what azoles are cleared by hepatic metabolism?

A

ketoconazole
itraconazole
voriconazole

23
Q

which azole is cleared by renal elimination?

A

fluconazole

24
Q

side effects of azoles

A

GI symptoms, skin rash
hepatotoxicity (rare)
visual disturbances (voriconazole)
↓ synthesis of steroid hormones cortisol and testosterone –> ↓ libido, gynecomastia (ketoconazole)

25
Q

clinical use of ketoconazole

A
  1. Mucocutaneous candidiasis (topical)
  2. Dermatophytosis (topical)
  3. Cushing’s disease ( ↓ cortisol synthesis)
    * systemic use is limited cause of side effects
26
Q

clinical use of clotrimazole and Miconazole

A

topical: dermatophytes, superficial & vaginal candidiasis

OTC drug

27
Q

clinical use of fluconazole

A
  1. esophageal, oropharyngeal, vaginal and invasive candidiasis
  2. Coccidiodes infections
  3. Cryptococcus meningitis- treatment and prophylaxis
28
Q

clinical use of Itraconazole

A
  1. Dimorphic fungi, Blastomyces and Sporothrix infections

2. 2nd line agent for Aspergillus, Coccidioides, Cryptococcus, Histoplasma

29
Q

clinical use of Voriconazole

A

Aspergillus infections

invasive candida infections (including sepsis)

30
Q

what is Flucytosine?

A

Antimetabolite

31
Q

mechanism of action of Flucytosine (5-FC)?

A

5-FC is converted to 5-FU by fungal cytosine deamiase —> 1. tri-phosphorylation, incorporated into fungal RNA
2. 5-FU forms 5-Fd-UMP –> inhibits thymidylate synthase–> thymine ↓ (inhibits DNA synthesis )

32
Q

when does resistance to Flucytosine (5-FC) emerge?

A

when used alone and not in combination with Amphotericin B

33
Q

Flucytosine is used in combination with….

A

Amphotericin B or triazole

used to treat Cryptococcal meningitis and invasive candidiasis

34
Q

how is Flucytosine given?

A

orally

35
Q

can Flucytosine enter the CNS?

A

yes

36
Q

what type of elimination does Flucytosine have?

A

renal

37
Q

side effects of Flucytosine (5-FU)

A
  1. bone marrow dysfunction (reversible)
  2. alopecia
  3. liver dysfunction
38
Q

what is Caspofungin and what the mechanism?

A

an Echinocandin

inhibit the synthesis of β (1-3)-glucan, a critical component of the fungal cell wall.

39
Q

how is Caspofungin given and what is it’s T1/2?

A

IV

T1/2 9-12 h’

40
Q

metabolism of Caspofungin

A

hepatic

41
Q

clinical uses of Caspofungin

A
  1. candida infections failed to respond to amphotericin B (disseminated and mucocutaneous infections)
  2. mucor infection
  3. Aspergillus infection
42
Q

side effects of Caspofungin

A
  1. GI distress
  2. fever, headaches, flushing, skin rash
  3. hepatotoxic (rarely)
43
Q

what are Griseofulvin and Terbinafine?

A

systemic drugs for superficial fungal infections (cutaneous mycoses- dermatophytosis, onychomycosis)

44
Q

which systemic drug is an inducer of CYP450 enzymes?

A

Griseofulvin

↑ warfarin metabolism

45
Q

mechanism of action of Griseofulvin

A
  1. fungistatic effect
  2. accumulates in keratin-rich tissues
  3. interfere with microtubules function in dermatophytes
46
Q

resistance mechanism of Griseofulvin

A

↓ drug uptake

47
Q

clinical use of Griseofulvin

A

Dermatophytosis of the skin and hair

*not commonly used!

48
Q

how is Griseofulcin given?

A

orally

49
Q

how is Terbinafine given?

A

topically and orally

50
Q

side effects of Griseofulvin

A 
GI distress
headaches, mental confusion 
photosensitivity
hepatotoxicity 
Disulfiram-like reaction 
teratogenic
carcinogenic
51
Q

mechanism of action of Terbinafine

A
  1. fungicidal effect

2. inhibits squalene epoxidase–> interfering with ergosterol synthesis

52
Q

clinical use of Terbinafine

A
  1. Onychomycosis

2. Dermatophytosis of the skin and hair

53
Q

side effects of Terbinafine

A

GI distress
Headache, rash
hepatotoxicity
taste disturbances

Pharma 2nd semester (49 decks)

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