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► Med - Pharmacology > Anti-Fungal Agents > Flashcards

Anti-Fungal Agents Flashcards

1
Q

What has the broadest spectrum of all anti-fungal agents?

A

Amphotericin B

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2
Q

Amphotericin B ROA

A

IV - not orally absorbed

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3
Q

What is Amphotericin B standard of care for?

A

Life threatening fungal infections

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4
Q

What are the problems with Amphotericin B?

A

It has significant adverse side effects

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5
Q

Amphotericin B MOA

A
  • Ampho B binds to ergosterol in fungal membrane

- Forms pore in the membrane thereby increasing membrane permeability

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6
Q

How is amphotericin B specific for fungi?

A

Binds to ergosterol but only weakly to cholesterol so it does not affect host cells as much

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7
Q

What is the only fungi amphotericin B is not effective against?

A

Pseudallescheria boydii

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8
Q

What is amphotericin B resistance associated with?

A

Decreased ergosterol in the cell membrane

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9
Q

What is the typical regimen of therapy for amphotericin B?

A

Used as an initial induction therapy (typically 4 weeks) to reduce fungal burden, then replaced by newer, less toxic AZOLE drugs for consolidation therapy and prevention of relapse

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10
Q

What is the treatment of choice for Zygomycosis/mucormycosis?

A

Amphotericin B

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11
Q

What is the only anti-fungal agent approved for pregnant and breastfeeding women?

A

Amphotericin B

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12
Q

Amphotericin B SE

A
  • Fever, chills, muscle spasms, vomiting, headache and hypotension
  • Nephrotoxicity
  • Hepatotoxicity
  • Anemia
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13
Q

Flucytosine Pharmokinetics

A
  • Good oral bioavailability

- Good penetration into the CSF

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14
Q

What does the CSF penetration of flucytosine make it useful in treating?

A

Cryptococcus meningitis

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15
Q

Is dosage adjustment of Flucytosine required in renal failure?

A

Dosage adjustment required in presence of renal insufficiency

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16
Q

Flucytosine MOA

A

Taken up via cytosine permease and converted by fungal-specific cytosine deaminase to 5-FU analogs that inhibit thymidylate synthase (DNA synthesis) and RNA synthesis

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17
Q

Spectrum of Action of Flucytosine

A
  • Cryptococcus neoformans
  • Candida sp
  • Agents of chromoblastomycosis
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18
Q

Why is the use of flucytosine restricted?

A

Acquired resistance is very high

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19
Q

How does amphotericin B interact with flucytosine?

A

Ampho B enhances fungal cell uptake of flucytosine as it generates pores in the fungal cell wall

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20
Q

Flucytosine SE

A
  • GI effects
  • Bone marrow toxicity
  • Anemia
  • Teratogenic
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21
Q

What are the 2 groups of -azole drugs and what are the drugs in each class?

A

Imidazoles
- Ketoconazole (prototype)

Triazoles

  • Fluconazole
  • Itraconazole
  • Voriconazole
  • Posaconazole
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22
Q

What is the general spectrum of activity of all of the -azoles?

A

All have some activity against Candida and Cryptococcus

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23
Q

What is the order of the azoles from narrowest in spectrum to broadest spectrum?

A

Fluconazole - Itraconazole - Voriconazole - Posaconazole

24
Q

Why do -azoles have a large potential for drug interactions?

A

They are all major inhibitors of CYP450

25
Q

-azole MOA

A

Inhibit 14α􏰇-sterol demethylase involved in the biosynthesis of ergosterol, an essential component of fungal membranes

26
Q

-azole SE

A
  • GI Distress
  • Hepatotoxicity- requires hepatic enzyme monitoring
  • Can cause fetal abnormalities
27
Q

Which -azoles are related to the most drug interactions?

A

Most drug interactions are associated with Itraconazole and Voriconazole

28
Q

Itraconazole and Voriconazole Contraindications

A

Itraconazole and Voriconazole should NEVER be given to a patient taking STATINs due to increased risk of developing fatal Rhabdomyolysis

29
Q

Ketoconazole Pharmokinetics

A
  • Oral ketaconazole requires acidic environment for absorption
  • Poor penetration into CSF and urine
30
Q

Fluconazole Pharmokinetics

A

Good oral bioavailability and Excellent penetration into the CSF

31
Q

What drug has the fewest drug interactions of all the -azoles?

A

Fluconazole

32
Q

Fluconazole SE

A
  • Nausea, headache, skin rash and GI

- Alopecia (reversible) associated with long duration/high dose therapy

33
Q

Why is fluconazole useful for fungal bladder infections?

A

80% of drug eliminated unchanged in the urine

34
Q

Itraconazole Pharmokinetics

A

Poor penetration of CSF, urine and eye

35
Q

Itraconazole SE

A
  • Triad of Hypertension, Hypokalemia and Peripheral Edema

- Can cause CHF in patients with ventricular dysfunction

36
Q

Voriconazole Pharmokinetics

A

Well absorbed, broadly distributed into tissues including CSF - bioavailability is unpredictable and affected by genetic polymorphisms

37
Q

What is unique about the metabolism of voriconazole?

A

Non-linear metabolism - 50% increase in dose =􏰆 150% increase in serum concentration

38
Q

What is the treatment of choice for invasive Aspergillus?

A

Voriconazole

39
Q

Voriconazole SE

A
  • Periostitis
  • Transient vision changes
  • Photosensitivity/Rash- rarely Stevens Johnson syndrome

ONLY with very high doses

  • Visual/Auditory hallucinations
  • Seizures
40
Q

Posaconazole Pharmokinetics

A

Readily distributes to tissues, but POOR penetration of CSF and URINE

41
Q

What is the only azole effective VS Zygomycosis/Murcormycosis?

A

Posaconazole

42
Q

What are the Echinocandins?

A

Caspofungin
Micafungin
Anidulafungin

43
Q

Echinocandin Pharmokinetics

A

Poor penetration of CSF

44
Q

Echinocandin SE

A

Well tolerated- few adverse effects

  • Histamine-like effect (skin itching)- associated with rapid infusion
  • Embryotoxic- NOT TO BE USED IN PREGNANCY
45
Q

Echinocandin MOA

A

Echinocandins competitively inhibit 􏰃ß(1-3)-D-glucan synthase complex involved in the biosynthesis of the principal building block of the fungal cell wall

  • impairs structural integrity of fungal cell wall
  • increases osmotic instability leading to cell death
46
Q

What do echinocandins lack activity against?

A

Cryptococcus or dimorphic fungi

47
Q

Griseofulvin Clinical Use

A

Only clinical use is for the treatment of mycotic infections of the skin, nail and hair due to dermatophytes:

Microsporum, Epidermophyton & Trichophyton

48
Q

Griseofulvin MOA

A

The drug is fungistatic and binds to fungal microtubules, preventing the formation of the mitotic spindle and inhibiting fungal mitosis

49
Q

Terbinafine Clinical Use

A
  • Activity is limited to dermatophytes and Candida albicans

* Used in the treatment of tinea captis, tinea corpis, tinea cruis, tinea pedis and onchomycosis

50
Q

Terbinafine MOA

A

Inhibition of fungal SQUALENE EPOXIDASE in membrane synthesis which leads to a build up of squalene which is toxic to the fungal cells

51
Q

Nystatin MOA

A

Binds to ergosterol and forms pores in the fungal membrane - like ampho B

52
Q

Nystatin ROA

A

Too toxic for IV - only in gels, creams and ointments

53
Q

What is nystatin not active against?

A

Not active against dermatophytes

54
Q

opical Azoles: Clotrimazole, Miconazole and Terconazole Clinical Uses

A

Oral and Vulvovaginal candidiasis

Dermatophyte infections

55
Q

Topical Allylamines: Terbinafine and Naftifine and Benzylamines: Butenafine Clinical Uses

A

Candida albicans and dermatophytes

- Used in the treatment of tinea cruris, tinea corporis and tinea pedis

► Med - Pharmacology (74 decks)

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