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Y2 Pharmaco > Anti-fungal & Anti-Protozoal > Flashcards

Anti-fungal & Anti-Protozoal Flashcards

1
Q

List the Anti-fungals for systemic & subcutaneous mycotic infections.

A
  1. Amphotericin B
  2. 5-Flucytosine (antimetabolite antifungals)
  3. Echinocandins
    - caspofungin, micafungin, anidulafungin
  4. Azole antifungals - Triazoles
    - fluconazole, itraconazole, voriconazole
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2
Q

List the Anti-fungals used for Cutaneous infections.

A
  1. Nystatin
  2. Azole antifungals - Imidazoles
    - clotrimazole, miconazole
  3. Squalene epoxidase inhibitors - Terbinafine
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3
Q

[T/F] Inhaled corticosteroids can increase the risk for oral candidiasis

A

True

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4
Q

Name the Polyene Anti-fungals.

A
  1. Amphotericin B
  2. Nystatin
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5
Q

MOA of Polyenes.

A

Binds to ergosterol & causes pores to develop in the cell membrane

  • ergosterol is a principle sterol in the fungal cell membrane
  • pores disrupt membrane function
  • leaky cell => cell death
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6
Q

Name the 2 Azole antifungals.

A
  1. Triazoles (subcutaneous & systemic)
  2. Imidazoles (cutaneous)
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7
Q

MOA of Azoles

A

inhibition of ergosterol biosynthesis => disrupts membrane structure & function

Inhibits lanosterol 14- demethylase, thereby blocking the demethylation/conversion of lanosterol to ergosterol

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8
Q

MOA of Amphotericin B

A
  • lipophilic molecule that binds to ergosterol in plasma membrane => disrupts membrane function => cell death
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9
Q

Amphotericin B is often used against?

A

Often used in oral candidiasis & denture related-erythematous candidiasis in a variety of oral formulations

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10
Q

What is the antifungal spectrum of Amphotericin B?

A

Effective against
- candida albicans
- cryptococcus neoformans
- many strains of Aspergillus

*fungicidal or fungistatic depending on conc.

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11
Q

Administration of Amphotericin B.

A

Poor oral bioavailibility, thus

  1. slow IV infusion
    - if administered too fast => infusion related toxicity (fever & chills)
  2. Topical
    - e.g. even if its an oral mouthwash, its topical, it cannot enter system via GI
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12
Q

What are the 2 formulations of Amphotericin B.

A
  1. Sodium deoxycholate
    - conventional
    - cheaper
    - higher risk of renal toxicity
  2. Liposomal preparation
    - much much pricier
    - reduced risk of renal toxicity
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13
Q

Clearance of Amphotericin B.

A

Low levels of drug & its metabolites appear in urine over a long period of time, some also eliminated via bile

  • total daily dose of amphotericin B is decreased 50% when conventional amphotericin B causes renal dysfunction
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14
Q

List out the ABs and antifungals that are nephrotoxic.

A
  1. Aminoglycoside
  2. Vancomycin
  3. Amphotericin B
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15
Q

Briefly list out the adverse effects of Amphotericin B.

A
  1. Fever & chills (infusion related toxicity)
  2. Nephrotoxicity
    - despite low levels excreted in urine
    - conventional ampho B causes renal vasoconstriction, reduce GFR by more than half
    - px must be adequately hydrated
  3. Hypotension
  4. Thrombophlebitis
  5. Bone marrow suppression
  6. Ototoxicity
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16
Q

Name the antifungals that are safe during pregnancy.

A
  1. Amphotericin B (Cat B) (systemic)
  2. Terbinafine (Cat A - vaginal, Cat B - oral) (topical)
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17
Q

Name the antifungal that interferes w DNA synthesis.

A

5-Flucytosine

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18
Q

Which antifungal is never given as monotherapy?

A

5-Flucytosine
- always administered in combination w another antifungal due to high fungal resistance to it

Gold standard treatment (candidiasis & cryptococcal meningitis): when administered w amphotericin B

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19
Q

How is 5-FC administered?

A

Orally.
Good oral bioavailibility + penetrates well into CSF

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20
Q

5-FC is fungi_______.

A

Fungistatic

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21
Q

5-FC has a _______ fungal spectrum

A

Narrow fungal spectrum.
- some fungi lack cytosine deaminase

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22
Q

Briefly list the adverse effects of 5-Flucytosine.

A
  1. Bone marrow suppression
  2. GI effects
  3. Hepatotoxicity
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23
Q

What are the ABs & antifungals that most likely cause bone marrow suppression.

A
  1. Linezolid
  2. 5-Flucytosine
  3. Amphotericin B
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24
Q

Can 5-FC be given during pregnancy?

A

No. Cat C

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25
Q

List out the 3 echinocandins.

A
  1. Caspofungin
  2. Micofungin
  3. Andiulafungin
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26
Q

MOA of Echinocandins.

A

Targets cell wall synthesis, inhibits glucan synthase complex
- loss of structural integrity of cell wall

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27
Q

[T/F] Echinocandins are often administered orally.

A

False
- they lack oral bioavailability
- administered IV

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28
Q

Which antifungal is often given first line?

A

Echinocandins
- potent activity against Aspergillus & most Candida species
- including Azole resistant species (2nd line for invasive aspergillosis)
- good safety profile, adverse effects minimal
- useful for pxs who cannot tolerate amphotericin B (due to nephrotoxicity)

Downside: Cat C in pregnancy

29
Q

Metabolism & excretion of Echinocandins.

A
  • non renally cleared drug => no need for dosage adjustments in pxs w renal impairment
  • metabolised & eliminated in both urine & faeces
  • not metabolized by CYP450 enzymes => much lesser DDI than Azoles
30
Q

Azoles are predominantly fungi_____.

A

Fungistatic

31
Q

Name the 3 Triazoles.

A
  1. Fluconazole
  2. Itraconazole
  3. Voriconazole
32
Q

With which antifungal are we worried about Cardio-toxicity?

A

Itraconazole

33
Q

With which Antifungal are we worried about DDI?

A

Azoles
- targets CYP450 enzyme

34
Q

Which antifungals have oral bioavailability?

A
  1. 5-flucytosine (good)
  2. Triazoles (good)
  3. Terbinafine (some)
35
Q

Which antifungal interferes w squalene conversion?

A

Terbinafine

  • blocks biosynthesis of ergosterol much higher up the chain
  • accumulation of toxic amts of squalene => increased membrane permability & death of fungal cell
36
Q

Which is the only cutaneous antifungal that has oral bioavailiibity?

A

Terbinafine
- needs to be taken orally to treat 1. Dermatophyte onychomycoses (fungal infection of nails) 2. Tinea capitis (infection of scalp)
- drug needs to accumulate in the keratin to be effective
- wont work if applied topically

37
Q

What is the gold standard antifungal tx for Cryptococcus neoformans (meningitis)

A

Amphotericin B & 5-FC

  • in resource poorer countries => fluconazole
38
Q

Which antifungal is associated w neurotoxicity & visual disturbances/hallucinations.

A

Voriconazole.

39
Q

First line treatment for invasive aspergillosis

A

Voriconazole

40
Q

Which Triazoles have good CSF penetration?

A

Fluconazole & Voriconazole
F: CSF conc can reach 50-90% of plasma serum levels
V: good CSF penetration

Itraconazole has poor CSF entry

41
Q

How are Triazoles excreted.

A

Mostly renal clearance, in urine

  • itraconazole is excreted in faeces & urine
42
Q

Can Azoles be used during pregnancy?

A

No, Teratogenic.

Cat C: fluconazole & itraconazole
Cat D: voriconazole

43
Q

What are some possible DDIs w Azoles.

A
  • all azoles inhibit the hepatic CYP450 3A4 isoenzyme
  • may enhace activity of drugs metabolised by CYP450
  • including warfarin, cyclosporine & oral hypoglycemic agents
44
Q

How does resistance to Azoles occur?

A
  • mutations in the C-14 α-demethylase gene that leads to decreased azole binding.
  • some fungal strains: developed efflux pumps that pump azole out of the cell
45
Q

Which are the antifungals that are administered parenterally for systemic/subcutaneous treatment?

A
  1. Amphotericin B
  2. Echinocandins
46
Q

Name the 2 Imidazoles

A
  1. Clotrimazole
  2. Miconazole
47
Q

How are Imidazoles administered?

A

Topical application
E.g. lotion, cream, powder, pessary, lozenge

48
Q

Which antifungal has a cure rate of >80% for vulvovaginal candidiasis?

A

Clotrimazole

49
Q

What are some antifungals used to treat denture-related erythematous candidiasis?

A
  1. Clotrimazole/Miconazole
    - thin layer of clotrimazole cream can be applied to the tissue side of denture base
  2. Amphotericin B (in oral formulation)
  3. Nystatin? (It is used for cutaneous & oral candida infections)
50
Q

What condition heightens the risk of Candida infections?

A

Type 2 diabetes

51
Q

What are some adverse effects of Imidazoles?

A
  1. Topical use: contact dermatitis, vulvar irritation, edema
  2. Oral use: GI disturbances
52
Q

How can denture related-erythmatous candidiasis be helped?

A
  1. Denture hygiene:
    - thorough daily brushin
    - soaked overnight in antiseptic soln
    -> helps w prolonged periods of removal => minimized irritation
  2. Assess fit, OH, immune status, medications
  3. Use of disinfectant soln like chlorhexidine => reduce risk of candidiasis
53
Q

Which antifungal is given as a ‘swish and swallow/spit’ administration.

A

Nystatin
- for treatment of oropharyngeal candidiasis (thrush)

Nystatin can also be given intravaginally for vulvovaginal candidiasis or topically for cutaneous candidiasis

54
Q

What is nystatin commonly prescribed for?

A

Broad spectrum cutaneous antifungal
- commonly used to treat oral or GI fungal infections
E.g. cutaneous & oral candida infections
- topical application for denture stomatitis

55
Q

Which antifungal is active against trichophyton?

A

Terbinafine

  • trichophyton is a genus of fungi that causes tinea infections
56
Q

Clearance and excretion of Terbinafine.

A
  • extensively metabolized by several CYP450 isoenzymes
  • excreted mainly via urine
  • shd be avoided in pxs w moderate to severe renal impairment or hepatic dysfunction
57
Q

Can Terbinafine be prescribed during pregnancy?

A

Yes
Vaginal - Cat A
Oral - Cat B

58
Q

Name the anti-protozoal agent (in our syllabus)

A

Metronidazole

59
Q

What drugs are commonly used in localised and aggressive periodontitis

A

Metronidazole w Amoxicillin/Augmentin or Ciprofloxacin

  • also used in other anaerobic infections
60
Q

How is Metronidazole administered?

A
  • good oral bioavail
  • completely & rapidly absorbed after oral administration
61
Q

Distribution of Metronidazole?

A
  • distributes well through body
  • penetrates CSF
62
Q

How is Metronidazole metabolised & eliminated?

A

Metabolism:
- hepatic oxidation & metabolism
- rate of metabolism can be affected w concomitant tx w inducers/inhibitors of CYP450 (DDI)
- accumulates in px w severe hepatic disease

Elimination:
- parent drug & metabolites => excreted in urine

63
Q

List some adverse effects of Metronidazole?

A
  1. GIT effects: nausea, vomiting, epigastric distress, abdominal cramps (GIT effects most common)
  2. Unpleasant, metallic taste (H.pylori pxs complain about this)
  3. Urine turns dark or reddish-brown
    Etc etc
64
Q

Can Metronidazole be used in pregnancy?

A

Yes, Cat B

65
Q

What is Metronidazole useful for, aside from anti protozoal effects?

A

Excellent coverage against anaerobes! (Best bet for anaerobes)

Commonly used for:
1. Localised/aggressive periodontitis
2. Dentoalveolar abscess & pericoronitis
3. Anaerobes such as bacteroides species or CDAD
4. H.pylori (part of triple therapy)
5. Surgical prophylaxis (30-60 mins b4 incision)

& 6. Amebic infections caused by protozoa

66
Q

What are some common DDIs we shd warn patient about when taking Metronidazole?

A
  • may potentiate effects of warfarin
  • avoid taking alcohol
66
Q

What are some common DDIs we shd warn patient about when taking Metronidazole?

A
  • may potentiate effects of warfarin
  • avoid taking alcohol
67
Q

Why is Metronidazole useful against anaerobes?

A
  • serves as e acceptor, forms reduced cytotoxic free radicals that result in protein & DNA damage
68
Q

Name some drugs that are effective against anaerobes

A
  1. Metronidazole
  2. 3rd gen cephalosporins onwards
  3. Clindamycins

Y2 Pharmaco (22 decks)

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