C.4. Antifungal agents Flashcards
list 2 Polyenes
Amphotericin B and Nystatin
mechanism of action of Amphotericin B and Nystatin
- interact with ergosterol in fungal membranes to form ‘pores’, which disrupt membrane permeability
- Fungicidal effect
what is the basis of Amphotericin and Nystatin resistance?
strains that have low ergosterol content in their cell membranes are resistant
spectrum and clinical use of Amphotericin B
broadest antifungal spectrum.
systemic infections: Aspergillosis, Blastomyces, candida, Cryptococcus, Histoplasma, Mucor, Sporthrix
clinical use of Nystatin
topical for candidiasis
*systemic use is limited due to toxicity
how is Amphotericin given?
IV or orally (poor availability)
what is the T1/2 of Amphotericin B?
up to 2 weeks
does Amphotericin B have CNS penetration?
poor
an intrathecal injection is required against cryptococcal or candida meningitis
clearance of amphotericin
hepatic metabolism and renal elimination
adverse effects of Amphotericin infusion-related
fever, chills
muscle spasm
injection site phlebitis
hypotension (due to histamine release)
adverse effects of Amphotericin dose-dependent
- nephrotoxicity (↓ GFR, RTA, K and Mg² wasting, ↓EPO)
- CNS toxicity (seizures)
- Anemia
what are the means to reduce infusion-related toxicity with Amphotericin administration (4)?
- anti-histamines
- NSAID’s
- Meperidine- opioid
- Corticosteroids
what are the means to reduce dose-dependent toxicity with Amphotericin administration (4)?
- liposomal formulation of Amphotericin B
- Co-administration with flucytosine
- volume expansion with IV saline
- K and Mg² supplementation
mechanism of action of azoles
- interfere with the synthesis of ergosterol
2. Fungicidal effect
resistance mechanism of azoles
develops with long term use via ↓ intracellular accumulation and altered sensitivity of target enzymes
what are ketoconazole, clotrimazole and Miconazole?
Imidazoles
what is Fluconazole and Itraconazole?
1st generation Triazoles
what is Voriconazole?
2nd generation Triazole
how are azoles given?
oral, parenteral, topical
which azole can penetrate the CSF and cross the BBB?
fluconazole
are azoles inhibitors of CYP450 enzymes?
yes