B3-046 - Fungal Drugs Flashcards
Membrane-active agents
Amphotericin B
Nystatin
Cell wall synthesis inhibitors
Caspofungin
Azole derivatives
Ketoconazole
Itraconazole
Fluconazole
Voriconazole
Antimetabolite
Flucytosine
Microtubule poison
Griseofulvin
Allyl amines
Terbinafine
Flucytosine mechanism
Activated by fungal cytosine deaminase
converted to 5-fluorouracil (5-FU) which blocks DNA and RNA synthesis by inhibiting thymidylate synthase
Flucytosine pharmacokinetics
Orally effective, well distributed, including CNS
Excreted in urine
Flucytosine adverse effects
Low tax to patients (not activated in mammalian cells)
Flucytosine clinical uses
Narrow spectrum - cryptococcus, some candida
Resistance develops rapidly, use only with amphotericin B or -azoles
Fungi use ____ instead of cholesterol
Ergosterol
Amphotericin B mechanism
Polyene macrolide anti fungal - binds to ergosterol in fungal membrane - makes plasma mem leaky and cell dies from pore formation and leakage
Amphotericin B Pharmacokinetics
Must give IV or direct to CNS
widely distributed (IV doesn’t cover CNS)
very slow excretion (t-1/2 = 2 weeks)
Amphotericin B should be administered _____ due to its slow excretion time
Low and slow (infusion, slow IV drip)
Liposomal Amphotericin B
Liposomal reservoir of amphotericin. Increases effectiveness, decreases toxicity
Affinities of amphotericin B for Fungal membranes, liposome, and human membrane
Fungal mem - 10
Liposome - 1
Human mem - 0.1
Amphotericin B clinical uses
Most important drug for mucous - cryptococcus meningitis, blastomyces, candida, coccidoides, more
Broad spectrum antifungal
Use for initial intervention, then switch to other anti-fungals for maintenance/cure
Amphotericin B adverse effects
“Ampho-terrible B”
Shake and Banke
- chills, fever, nausea, vomiting, headache
usually medicate to suppress adverse effects
Common irreversible nephrotox
Nystatin mechanism
Similar to amphotericin B
too toxic for systemic use
Nystatin is given ____ to treat ____
orally - “swish and swallow”.
pseudo-topical treatment for Candidas
Nystatin adverse effects
Diarrhea, nausea, sometimes Stevens Johnson rash
Terbinafine is administered
Orally (as griseofulvin) or topical
Terbinafine has a _____ bioavailability and a half life of __
Low. 2 weeks
Terbinafine mechanism
Inhibits squalene epoxidase (ergosterol synthesis)
This causes accumulation of squalene (toxic)
Mechanism of -azoles
Inhibit ergosterol synthesis by blocking fungal CYPs
This impacts all CYPs so is impacts other drug metabolism
Ketoconazole pharmacokinetics
1st effective oral anti fungal for systemic use
Absorbed and dist well, except for CNS
Ketoconazole adverse effects
Nausea, vomiting, anorexia
Hepatotoxicity
Blocks adrenal steroidogenesis (gynecomastia)
Inhibits drug metabolism - interacts with cyclosporin, and many other drugs
Ketoconazole is also used as an adjust therapy for _____
prostate cancer
Due to ketoconazole’s adverse effects, it is rarely used as _____, however ______ is available.
systemic anti fungal; topical therapy
Itraconazole is given
Orally (low bioavailability) and IV
Itraconazole has (more or less) effects on mammalian CYPs than ketoconazole
Less
Itraconazole clinical uses
histoplasma, blastomyces, sporothrix
Fluconazole pharmacokinetics
Most used anti-fungal
Oral and IV
Water soluble
High bioavailability, good CSF delivery
More selective for fungal CYPs
Fluconazole clinical uses
Cryptococcal meningitis, candidemia, mucocutaneous candidiasis
Vorizonazole pharmacokinetics
Newest triazole
IV or Oral (90% bioavailability)
Metabolism in liver, little mammalian CYP inhibition
Vorizonazole is better tolerated and more effective than _____ for treatment against ______
Amphotericin B; invasive aspergillus
Voriconazole adverse effects
Visual disturbances (30%)
Used for candida and dimorphic fungi
Caspofungin mechanism
Inhibits synthesis of B(1-3) gluten fo cell wall
Incomplete cell wall synthesis causes cell lysis
Caspofungin is given
IV, highly protein bound with slow metabolism
Caspofungin adverse effects
GI, flushing
Caspofungin clinical uses
Approved for Candida, emperic anti-fungal therapy
Salvage therapy for Amphotericin-resistant Aspergillus
Caspofungin memory tool
CAspoFunGIN
C- Candida
A - aspergillus
F - glushing
G - GI
IN - IV
Griseofulvin is given ____
orally, concentrates in keratinized tissue
Griseofulvin mechanism
Maybe blocks mitosis - still unknown
Griseofulvin clinical use
Treatment of ringwork athletes foot
Griseofulvin adverse effects
CYP inducer/teratogenic
Hepatotoxic