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PR3151 > Pharmacology- Antifungals > Flashcards

Pharmacology- Antifungals Flashcards

1
Q

What class of antifungals does amphotericin B belong to?

A

Polyenes

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2
Q

What class of antifungals does nystatin belong to?

A

Polyenes

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3
Q

How is amphotericin B administered?

A

Topical or (slow) IV

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4
Q

What is the spectrum of action of amphotericin B?

A

Effective against Candida albicans (Candidiasis), Histoplasma (Histoplasmosis), Cryptococcus and many species of Aspergillus (Asperigillosis)

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5
Q

Is amphotericin B able to penetrate the CSF?

A

Poor but improves w inflammation

Liposomal formulations are better at penetrating

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6
Q

How is amphotericin B excreted?

A

Low levels of parent & metabolites appear in the urine over a long period of time, and some also eliminated by bile

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7
Q

What are the adverse reactions associated with amphotericin B?

A
  1. Fever and chills - usually 1-3h after starting IV infusion, but usually subside w repeated admin of the drug
  2. Nephrotoxicity - low levels in urine but conventional formulation causes renal vasoconstriction, reducing GFR by more than half. Avoid concurrent Tx w other nephrotoxic agents. Ensure adequate hydration
  3. Hypotension w hypokalaemia: may need K supplementation, be cautious w K fluctuation causing drugs
  4. Thrombophlebitis - can add heparin to the infusion to alleviate
  5. Bone marrow suppression, anemia
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8
Q

How is nystatin administered?

A

PO/Topical

Not used parenterally due to systemic toxicity (acute infusion-related adverse effects and nephrotoxicity)

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9
Q

What is the spectrum of action of nystatin?

A

Effective against Candida albicans (Candidiasis), Histoplasma (Histoplasmosis), Cryptococcus and many species of Aspergillus (Asperigillosis)

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10
Q

What is nystatin used for?

A

Oropharyngeal candidiasis
Vulvovaginal candidiasis
Cutaneous candidiasis

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11
Q

What are the adverse effects associated with nystatin?

A

PO: rare to have adverse effects

Topical/Vaginal: skin irritation

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12
Q

What is the mechanism of action of azoles?

A

Inhibit C-14 a-demethylase (CYP450 enzyme), thereby blocking the demethylation of lanosterol to ergosterol.
Results in disrupted membrane structure and function, inhibits fungal cell growth

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13
Q

What is the difference in the use of triazoles vs imidazoles?

A

triazoles - used IV/PO
imidazoles - used topically or slow IV (v low PO absorption)

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14
Q

List the triazoles.

A

Fluconazole, Posaconazole, Itraconazole, Voriconazole

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15
Q

List the imidazoles.

A

Clotrimazole, miconazole

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16
Q

What is the spectrum of action of fluconazole?

A
  1. Candida infections and most forms of mucocutaneous candidiasis
  2. Cryptococcal meningitis (but not 1st line)
  3. Histoplasmosis
  4. Single, small dose PO Tx for vulvovaginal candidiasis
  5. Most types of fungal meningitis
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17
Q

What is the spectrum of action of posaconazole?

A

Coverage against multiple infections: Candida, Aspergillus, some species of Fusarium and zygomycetes

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18
Q

What is the spectrum of action of itraconazole?

A

Broad spectrum compared to fluconazole
Tx of histoplasmosis, blastomycosis, aspergillosis in pts intolerant to amphotericin B
Tx of onychomycosis in non immunocompromised pts
Oral solution used for esophageal & oropharyngeal candidiasis

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19
Q

What is the spectrum of action of voriconazole?

A

Broad-spectrum antifungal
For invasive apergillosis and candida infections

20
Q

Which of the triazoles can penetrate the CSF?

A

Small molecule triazoles can - fluconazole, voriconazole
Large molecule triazoles cannot - posaconazole, itraconazole

21
Q

How is fluconazole excreted?

A

Renal, unchanged

22
Q

How is posaconazole excreted?

A

Mainly by faeces

23
Q

How is itraconazole excreted?

A

Hepatic metabolism, parent drug and inactive metabolites excreted in faeces and urine

24
Q

How is voriconazole excreted?

A

Metabolised by CYP450s, inactive metabolites excreted by urine

25
Q

What are the adverse reactions associated with triazoles?

A
  1. N/V
  2. Headache
  3. Skin rashes
  4. Hepatotoxicity
  5. QT prolongation
26
Q

How should itraconazole capsules be taken?

A

Take after a full meal

27
Q

How should itraconazole solution be taken?

A

Take on an empty stomach

28
Q

What does voriconazole interact with?

A

Don’t take with PPIs - Voriconazole is metabolized by CYP2C19 and proton-pump inhibitors are enzymatic inhibitors of CYP2C19.

29
Q

What is the spectrum of action of imidazoles?

A

Wide range of activity against Epidermophyton, Microsporum, Trichophyton, Candida and Malassezia (depending on agent)
Generally used for Tinea and candidiasis

30
Q

What indications are clotrimazole used for?

A

Dermatophyte infections
Cutaneous candidiasis
Vulvovaginal candidiasis
Oral and pharyngeala candidiasis (troches)

31
Q

What indications are miconazole used for?

A

Tinea pedis, tinea cruris, tinea versicolor, vulvovaginal candidiasis

32
Q

What are the adverse effects associated with the imidazoles?

A

Topical use associated w contact dermatitis, vulvar irritation and edema

Oral admin may result in GI disturbances

33
Q

Name the echinocandins.

A

Caspofungin, Micafungin, Anidulafungin

34
Q

What is the mechanism of action of echinocandins?

A

Inhibits activity of glucan synthase complex, so that synthesis of glucans to make up fungal cell wall is inhibited, to result in loss of structural integrity of cell wall and thus cell lysis

35
Q

How are the echinocandins administered?

A

IV

36
Q

What is the spectrum of action of the echinocandins?

A

Potent activity against Aspergillus and most Candida species, incl azole resistant species

1st line for invasive candidiasis, 2nd line for invasive aspergillosis in pts that have failed or cannot tolerate amphotericin B or an azole

37
Q

Are the echinocandins able to penetrate the CSF?

A

No.

38
Q

How are the echinocandins excreted?

A

Metabolised slowly by hydrolysis and N-acetylation, not metabolised by CYP450 but DDI observed for micafungin

Non-renally cleared

39
Q

What are the adverse reactions associated with the echinocandins?

A

Minimal, rarely lead to drug discontinuation
1. GIT Sx
2. Fever, chills
3. Rashes
4. Skin flushing
5. Thrombocytopenia

40
Q

What is the mechanism of action of terbinafine?

A

Inhibit squalene epoxidase to block conversion of squalene to lanosterol and biosynthesis of ergosterol

Accumulation of toxic amounts of squalene results in inc membrane permeability and death of the fungal cell

41
Q

How is terbinafine administered?

A

PO/Topical

42
Q

What is the spectrum of action of terbinafine?

A

Active against Trichophyton

PO used to treat nail fungal infections and tinea capitis (needs to accumulate in keratin to exert effect)

Topical used to treat tinea pedis, tinea corporis and tinea cruris

43
Q

In what groups of patients should PO terbinafine be avoided in?

A

Moderate-severe renal impairment or hepatic dysfunction

44
Q

How is PO terbinafine excreted?

A

PO extensively metabolised by several CYP450s

Excreted mainly by urine

45
Q

What are the adverse reactions associated with terbinafine?

A
  1. GI disturbances
  2. Headache
  3. Rash
  4. Elevated liver enzymes

PR3151 (14 decks)

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