Antifungals Flashcards
Polyene antibiotic that binds to Ergosterol and forms pores in the cell wall, leading to ion leakage and cell death
Amphotericin B
Antifungal agent with the broadest spectrum of activity, including fungicidal
Amphotericin B; used against yeasts, endemic mycoses, and pathogenic molds
Highly insoluble and formulated as deoxycholate colloidal suspension
Amphotericin B
PK of Amphotericin B
Slow IV infusion (poor oral absorption); Low penetration into CSF; Intrathecal for Meningeal disease
Often used as initial induction regimen to reduce fungal burden, then followed by an Azole
Amphotericin B
Preferred treatment for deep fungal infections during prenancy
Amphotericin B
AE of Amphotericin B
Infusion-related: fever and chills, muscle spasms, vomiting, headache, hypotension
Anemia due to decreased Erythropoietin
Premedication with which drugs may alleviate AE of Amphotericin B?
Antihistamines, Glucocorticoids, Antipyretics, or Meperidine
How does Amphotericin B cause renal toxicity?
Slow toxicity by binding Cholesterol and forming pores in the mammalian cell membranes
How can renal damage by Amphotericin B be attenuated?
Administration of Saline infusion with Amphotericin B
What should be monitored during Amphotericin treatment?
Liver and Kidney function, serum electrolytes (Mg and K), blood counts, and hemoglobin
How does Amphotericin B affect the CNS?
Slow toxicity: Intrathecal administration can cause seizures and neurological damage
3 Lipid formulations of Amphotericin B
Liposomal Amphotericin B (L-AMB)
Amphotericin B Lipid Complex (ABLC)
Amphotericin B Colloidal Dispersion (ABCD)
Why are Lipid formulations of Amphotericin B used?
Packaging Amphotericin B in lipid carriers reduces exposure to nephron –> reduces nephrotoxicity
Synthetic Pyrimidine antimetabolite that uses Cytosine permease to enter fungal cells
Flucytosine
MOA of Flucytosine
Fungistatic; Enters fungal cell via Cytosine permease –> converted to 5-Fluorouracil (5-FU) —> converted to 5-fluorodeoxyuridine monophosphate –> inhibits thymidylate synthase –> no synthesis of dTMP.
Fluorouridine triphosphate (5-FUTP) is also formed –> inhibits protein synthesis
PK of Flucytosine
Mammalian cells cannot convert it into its active metabolites
Combination of Flucytosine and which drug gives a synergistic effect?
Amphotericin B
Nicknamed the “suicide inhibitor”
Flucytosine
Description of Flucytosine
Narrow spectrum; used in combination with other drugs for synergism and to avoid resistance
Which drug is combined with Amphotericin B to treat systemic candidiasis and cryptococcosis?
Flucytosine
Indications of Flucytosine
Candida and/or Cryptococcal infections
AE of Flucytosine
Bone marrow toxicity; due to metabolism by intestinal flora to 5-Fluorouracil
Triazoles
Itraconazole, Fluconazole, Voriconazole, Posaconazole
Imidazoles
Ketoconazole, Miconazole, Clotrimazole
Are Azoles used for Systemic or Superficial mycoses?
Systemic mycoses
Classifications of Azoles
Imidazoles and Triazoles
MOA of Azoles
Azoles inhibit CYP450 enzyme 14-alpha-sterol demethylase, which usually converts Lanosterol to Ergosterol –> disrupts membrane function and increases permeability
Specificity of Azoles is due to a greater affinity for fungal CYP450 enzymes than for human CYP450 enzymes. Which Azoles have greater specificity?
Triazoles
AE of Azoles
GI upset; relatively non-toxic
PK of Ketoconazole
Strong inhibitor of CYP3A4; can potentiate Warfarin and Cyclosporine toxicities
Poor CSF penetration
How do Antacids, H2-blocker, and PPIs affect Ketaconazole absorption?
Ketaconazole is best absorbed at low gastric pH; these drugs interfere with absorption