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Flashcards in Anti-fungal drugs Deck (12)
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1
Q

What is another name for a fungal disease?

A

‘mycoses’ - eukaryotes

  1. superficial mycoses affect:
    - scalp, nails, skin, mucous membranes (oral cavity and vagina)
    - not life-threatening (opportunistic pathogens)
  2. systemic mycoses affect:
    - internal organs (kidneys, lung, brain)
    - fatal in severely immuno-comprimised patients (become opportunistic pathogens)
2
Q

Most common opportunistic pathogens

A
Candida albicans (commensal)
Aspergillus fumigatus (environmental)
Cryptococcus neoformans (environmental)
3
Q

What puts patients at higher risk of fungal infections?

A
impaired immune system - 
- HIV/aids
- organ transplantation
- long term course of antibiotics
- premature birth
- cancer
- hospitalisation in ICU
menstrual cycle in women
4
Q

Targets for fungal cell treatment

A

cell wall - skeletal and matrix components
> skeletal cell wall contains B1-3 Glucan and Chitin
> matrix contains Mannan (protein)
plasma membrane
nucleus (DNA and RNA synthesis)

5
Q

Anti-fungals that inhibit the cell wall

A

Echinocandins

eg. Caspofungin, Micafungin

6
Q

What are the main differences between human and fungal plasma membranes?

A

PM’s in fungal cells contain ergosterol, those of human cells contain cholesterol
without ergosterol cells cannot survive and grow

7
Q

What are the 2 types of anti-fungal’s that target ergosterol?

A

some kill existing cells (bind to resident ergosterol in PM)

others inhibit new cell’s production

8
Q

Polyene antifungals

A

ergosterol inhibitor
polyenes are fungicidal
bind to engosterol and form pores in the plasma membrane
pores disrupt membrane integrity causing leakage of cell constituents
prolonged application associated with kidney failure
eg. Amphotericin B -
Nystatin - used in treatment of oral and GI fungal infections
both natural in origin

9
Q

Azoles

A

ergosterol inhibitor
are fungistatic
inhibits the enzyme Lanosterol C-14 demethylase
inhibition of the enzyme:
- blocks ergosterol biosynthesis
- leads to accumilation of toxic intermediates
- causes growth arrest
2 types:
- Imidazoles eg. Miconazole
- Triazoles eg. Fluconazole (more potent as higher affinity for enzyme)

10
Q

Allylamines

A

ergosterol inhibitor

eg. Terbinafine, Amorolfine

11
Q

RNA & DNA synthesis as targets for antifungals

A

eg. Flucytosine
- taken up by fungal cells
- metabolised by fungal cells by 5-fluorouracil (5-FU)
- 5-FU is a toxic anti-metabolite that inhibits DNA and RNA synthesis
- usually used in combination with azoles

12
Q

Anti-fungal resistance

A

caused by:

  • decreased accumulation of the drug
  • inactivation of the drug
  • mutations in drug target-encoding genes
  • biofilm formation (grwoth on catheters)