Pharm 36: Fungicidal Tendencies Flashcards
Flucystosine MOA
converted to 5-FdUMP within cell.
5-FdUMP inhibits thymidylate synthase, resulting in inhibtion of DNA synthesis
Flucytosine is fungi_____
Fungistatic
Why doesnt flucytosine affect human cells
No cytosine permeases expressed, drug can’t enter
Flycytosine used along with _____
Why?
Amphotericin B
Acts synergistically
Without Amphotericin, resistance emerges quickly
Single agent flucystosine used for
Candidiasis,
Cryptococcosis
Chromomycosis
Flucytosine tissue penetrance
Very high. CNS, eyes, urinary tract
Flucytosine AEs
Bone marrow suppression, hepatic dysfunction
DO NOT USE IN PREGNANCY
Griseofulvin MOA
Binds to tubilin and microtubules to disrupt mitotic spindle preventing mitosis
Griseofulvin is fungi___
Fungistatic
Griseofulvin accumulates in _____
Keratin precursor cells
Griseofulvin used for
Skin/hair/nail fungal infections
How to increase griseofulvin absorption
Eat with fatty (greasy) meal
Griseofulvin ____ P450
Enhances
What dose squalene epoxidase do?
Part of ergosterol synthesis
Converts squalene to lanosterol
Terbinafine MOA
Squalene epoxidase inhibitor
Terbinafine kinetics (oral)
Binds to plasma then goes through liver first pass metabolism.
Oral bioavailability 40%
300 hour half life
Terbinafine AEs
Hepatotoxicity, SJS, psoriasis
Terbinafine used for
Onychomycosis (nail fungus)
Use for all types of tinea
Terbinafine metabolism
Via P450
Naftifine MOA and use
Topical squalene epoxidase inhibitior
Used for tineas
Butenafine MOA and use
Squalene epoxidase inhibitors
Effective against tineas
14a-sterol demethylase: what does it do
Fungal enzyme that catalyses conversion of lanosterol to ergosterol
Azoles MOA
Inhibit fungal 14α-sterol demythylase.
Causes 14α-methyl to accumulate and disrupt the phospholipid membrane
Cell dies
Azoles are fungi___
Fungistatic (usually)
Ketoconazole AEs
Adrenal insuficiency, gynegomastia, impotence, androgen synthesis inhibition
Miconazole MOA
Inhiits 14α-sterol demethylase as well as fatty acid synthesis and peroxidase enzymes
Itraconazole use
Broad spectrum mycoses treatment
Itraconazole kinetics
Needs acidic environment for absorption, oxidized in liver to active form.
Plasma bound
Itraconazole in meningitis
Doesnt penetrate CSF but can reach meninges
Fluconazole kinetics
Gastric pH doesnt matter, 100% bioavilability, reaches everything (CSf, urine, saliva)
Drug of choice for systemic candidiasis, cryptococcal meningitis and coccidiodal meningitis
Fluconazole
Fluconazole resistance via
Mutation and overexpression of fungal P450 enzymes
Ravuconazole spectrum
Expanded spectrum fluconazole, works against aspergillius
Drug of choice for invasive aspergillosis, fusarium and scedosporium
Voriconazole
Voriconazole AEs
Hepatic toxicity
Visual symptoms
Terconazole
Vaginal suppository for vaginal candidiasis
Amphotericin B toxicity to humans via
Also affects human plasma membrane sterols
Amphotericin B MOA
Binds ergosterol to disrupt fungal membrane stability, forming pores
Also generates free radicals that further damage membrane
Nyastatin MOA
Binds ergosterol to disrupt fungal membrane stability
Natamycin MOA
Binds ergosterol to disrupt fungal membrane stability
Polyene MOA
Binds ergosterol to disrupt fungal membrane stability
Amphotericin fungicidal vs fungistatic depends on
Dose
Amphotericin B AEs
Systemic reactions: cytokine storm (fever, hypotension)
Renal: significant renal toxicity. Discontinue if BUN or creatinine rise too much. Hypokalemia common
Hematologic: anemia b/c decreased erythropoietin
How to reduce amphotericin B toxicity
Package in liposomes/ other lipid carriers
Nyastatin use
Used topically in skin, vaginal mucosa, oral mucosa
Doesn’t absorb
Natamycin use
Corneal infection with aspergillus or fusarium
Caspofungin, micafungin and anidulafungin MOA
Noncompetitive inhibition of β-(1,3)-D-glucans
This disrupts cell wall intergrity
Caspofungin use
Empiric for febrile neutropenia
Also candidiasis
Micafungal use
Esophageal candidiasis and antifungal prophylaxis in stem cell transplant
Ciclopirox MOA.
Chelates Fe3+ and Al3+ which inhibits many fungal processes
Ciclopirox use
Skin infections topically