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Anti-fungal & Anti-Protozoal Flashcards

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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
List out the 3 echinocandins.
1. Caspofungin 2. Micofungin 3. Andiulafungin
26
MOA of Echinocandins.
**Targets cell wall synthesis, inhibits glucan synthase complex** - loss of structural integrity of cell wall
27
[T/F] Echinocandins are often administered orally.
False - they lack oral bioavailability - administered IV
28
Which antifungal is often given first line?
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
Metabolism & excretion of Echinocandins.
- 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
Azoles are predominantly fungi_____.
Fungistatic
31
Name the 3 Triazoles.
1. Fluconazole 2. Itraconazole 3. Voriconazole
32
With which antifungal are we worried about Cardio-toxicity?
Itraconazole
33
With which Antifungal are we worried about DDI?
Azoles - targets CYP450 enzyme
34
Which antifungals have oral bioavailability?
1. 5-flucytosine (good) 2. Triazoles (good) 3. Terbinafine (some)
35
Which antifungal interferes w squalene conversion?
Terbinafine - blocks biosynthesis of ergosterol much higher up the chain - accumulation of toxic amts of squalene => increased membrane permability & death of fungal cell
36
Which is the only cutaneous antifungal that has oral bioavailiibity?
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
What is the gold standard antifungal tx for Cryptococcus neoformans (meningitis)
Amphotericin B & 5-FC - in resource poorer countries => fluconazole
38
Which antifungal is associated w neurotoxicity & visual disturbances/hallucinations.
Voriconazole.
39
First line treatment for invasive aspergillosis
Voriconazole
40
Which Triazoles have good CSF penetration?
Fluconazole & Voriconazole F: CSF conc can reach 50-90% of plasma serum levels V: good CSF penetration Itraconazole has poor CSF entry
41
How are Triazoles excreted.
Mostly renal clearance, in urine - itraconazole is excreted in faeces & urine
42
Can Azoles be used during pregnancy?
No, Teratogenic. Cat C: fluconazole & itraconazole Cat D: voriconazole
43
What are some possible DDIs w Azoles.
- all azoles inhibit the hepatic CYP450 3A4 isoenzyme - may enhace activity of drugs metabolised by CYP450 - including warfarin, cyclosporine & oral hypoglycemic agents
44
How does resistance to Azoles occur?
- 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
Which are the antifungals that are administered parenterally for systemic/subcutaneous treatment?
1. Amphotericin B 2. Echinocandins
46
Name the 2 Imidazoles
1. Clotrimazole 2. Miconazole
47
How are Imidazoles administered?
Topical application E.g. lotion, cream, powder, pessary, lozenge
48
Which antifungal has a cure rate of >80% for vulvovaginal candidiasis?
Clotrimazole
49
What are some antifungals used to treat denture-related erythematous candidiasis?
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
What condition heightens the risk of Candida infections?
Type 2 diabetes
51
What are some adverse effects of Imidazoles?
1. Topical use: contact dermatitis, vulvar irritation, edema 2. Oral use: GI disturbances
52
How can denture related-erythmatous candidiasis be helped?
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
Which antifungal is given as a ‘swish and swallow/spit’ administration.
Nystatin - for treatment of oropharyngeal candidiasis (thrush) Nystatin can also be given intravaginally for vulvovaginal candidiasis or topically for cutaneous candidiasis
54
What is nystatin commonly prescribed for?
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
Which antifungal is active against trichophyton?
Terbinafine - trichophyton is a genus of fungi that causes tinea infections
56
Clearance and excretion of Terbinafine.
- 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
Can Terbinafine be prescribed during pregnancy?
Yes Vaginal - Cat A Oral - Cat B
58
Name the anti-protozoal agent (in our syllabus)
Metronidazole
59
What drugs are commonly used in localised and aggressive periodontitis
Metronidazole w Amoxicillin/Augmentin or Ciprofloxacin - also used in other anaerobic infections
60
How is Metronidazole administered?
- good oral bioavail - completely & rapidly absorbed after oral administration
61
Distribution of Metronidazole?
- distributes well through body - penetrates CSF
62
How is Metronidazole metabolised & eliminated?
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
List some adverse effects of Metronidazole?
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
Can Metronidazole be used in pregnancy?
Yes, Cat B
65
What is Metronidazole useful for, aside from anti protozoal effects?
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
What are some common DDIs we shd warn patient about when taking Metronidazole?
- may potentiate effects of warfarin - avoid taking alcohol
66
What are some common DDIs we shd warn patient about when taking Metronidazole?
- may potentiate effects of warfarin - avoid taking alcohol
67
Why is Metronidazole useful against anaerobes?
- serves as e acceptor, forms reduced cytotoxic free radicals that result in protein & DNA damage
68
Name some drugs that are effective against anaerobes
1. Metronidazole 2. 3rd gen cephalosporins onwards 3. Clindamycins

Y2 Pharmaco (22 decks)

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