Antifungals Flashcards
Types of Fungal infections
- Superficial mycoses- Affects skin, mucous membranes, hair & nails
- Subcutaneous mycoses- Affects dermis, subcutaneous tissues & adjacent bone
- Systemic mycoses- Affects internal organs
MC Systemic fungal infections
- Candidiasis
- Cryptococcosis
- Aspergillosis
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Classification of Antifungals by MOA
- Alter cell membrane permeability
- Polyenes
- Azoles
- Allylamines - Block Nucleic acid synthesis
- Flucytosine - Disrupt microtubule function
- Griseofulvin - Disrupt fungal cell wall
- Echinocandins
Classification of Antifungals by Clinical use
- Drugs for Subcutaneous & Systemic mycoses
- Systemic drugs = Amphotericin B, Flucytosine, Azoles & Echinocandins - Drugs for superficial mycoses
- Systemic drugs
- Topical drugs
Amphotericin B MOA
Binds to Ergosterol –> Forms pores in cell membrane –> Leakage of intracellular ions & macromolecules –> Cell death
Amphotericin Activity
- Broadest spectrum
- Activity against Clinical significant yeasts, Organisms causing endemic mycoses & Pathogenic molds
Pharmacokinetics of Amphotericin B
- Highly insoluble
- Poor GI absorption = MUST be IV
- Low CSF Penetration = Intrathecal therapy necessary for meningitis
Uses of Amphotericin B
- Nearly all life-threatening fungal infections
- Used as initial induction to rapidly reduce fungal burden –> Pts, then continue w/ an azole
Infusion- related AEs of Amphotericin B
Other/ Slow toxicity AEs of Amphotericin B
Lipid formulations of Amphotericin B
Developed to reduce Nephrotoxicity
- Liposomal Amphotericin B (L-AMB)
- Amphotericin B Lipid Complex (ABLC)
- Amphotericin B colloidal Dispersion (ABCD)
MOA of Flucytosine
Taken up by fungal cells via Cytosine Permease –> Converted intracellularly to 5-flurouracil (5-FU) –> Converted to 5-fluorodeoxyuridine monophosphate (5-FdUMP)
- Also forms Fluorouridine Triphosphate (5-FUTP)
Actions of %- Fluorodeoxyuridine Monophosphate (5-FdUMP)
Inhibits Thymidylate Synthetase –> Blocks dTMP synthesis/ Inhibits DNA synthesis
Actions of Fluorouridine Triphosphate (5-FUTP)
Inhibits protein synthesis
Why is Flucytosine & Amphotericin B combined
Mammalian cells are unable to convert the parent drug to its active metabolite
Specrum of Flucytosine
- Fungistatic
- Narrow spectrum
- NEVER used as single agent - Avoid resistence
Uses of Flucytosine
- Serious infections caused by susceptible strains of Candida &/or Cryptococcus
USED w/ Amphotericin B to avoid resistance
AEs o Flucytosine
- Bone marrow toxicity
Results from metabolism to 5-fluorouracil
Classification & names of Azoles
MOA of Azoles
Inhibits 14-a-sterol demethylase –> Dec Ergosterol synthesis –> Disrupt membrane function –> Inc permeability