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Antibiotics simplified > Anti-fungals > Flashcards

Anti-fungals Flashcards

1
Q

yeast

A

solid forms of fungi that reproduce by budding

have moist, shiny appearance in colonies

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2
Q

moulds

A

branching hyphae, multicellular

can reproduce by translocation of existing hyphae to new area or through spore formation and spread

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3
Q

dimorphic fungi

A

mould at room temp

yeasts at body temp

endemic fungi: coccidiodes immitis in southwestern US and central california–> valley fever

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4
Q

problems of treating fungal infxn

A

1) infxn looks similar to bacterial infxn
2) most centers don’t conduct antifungal susceptibility testing
3) condition of immune system of host–> control risk factors is important

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5
Q

polyenes

A

amphotericin B deoxycholate, lipid formulation of AmB and nystatin (topical)

work by binding to ergosterol in cell membrane–> disrupting its function

nephrotoxicity and infusion related reactions

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6
Q

lipid forms of AmB

A

AmB colloidal dispersion (ABCD)

AmB lipid complex (ABLC)

liposomal AmB (LAmB)

less used after introduction of echinocandins and broad-spectrum azoles

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7
Q

spectrum of polyenes

A

Good: most candida spp, aspergillus, C neoformans, dimorphic fungi and many moulds

moderate: zygomycetes
poor: candida lusitaniae, aspergillus terreus

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8
Q

toxicity of polyenes

A

nephrotoxicity via direct damage to distal tubules–> Mg and K wasting and indirect damage via vasoconstriction of afferent arteriole

infusion-related reactions: fever, chill, rigors and less common rash and increased transaminases

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9
Q

AmB nephrotoxicity can be attenuated by

A

sodium loading: give boluses of normal saline before and after AmB treatment–> inexpensive

Can give acetaminophen, diphenhydramine and hydrocortisone to decrease incidence and severity of infusion-related reactions

Meperidine can be given to prevent rigors but it has a neurotoxic metabolite that can affect pt with renal dysfunction because it’s eliminated renally

ABCD has worst infusion-related reaction, LAmB has the least reaction. All have less nephrotoxicity than AmB deoxycholate, but LAmB is the least nephrotoxic

Nystatin is used topically due to poor tolerance when given systemically

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10
Q

AmB formulations best for

A

cryptococcal meningitis, dimorphic fungi and some mould infections

reasonable to give if fungal infxn is suspected but source is unknown–> febrile neutropenia

double check dose and which formulation ur using

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11
Q

anti-metabolites

A

flucytosine (5-FC)

interferes with DNA synthesis

used in combination with AmB formulations for cryptococcal disease

hight toxicity–> rarely used for other infxn

Good: also for most candida spp

moderate: monotherapy against C. neoformans and candida spp
poor: mould, candida krusei

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12
Q

AE of 5-FC

A

also called fluorouracil for fungi

BM suppresion especially in high doses or prolonged courses

GI complaints more common but less severe

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13
Q

5-FC drug monitoring

A

check peak concentration about 2 hrs after dose is given. Also measure hematology values

due to resistence–> don’t use as monotherapy

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14
Q

Azoles

A

inhibit fungal cytochrome P450–> decrease ergosterol production–> also issues with drug interactions

ketoconazole, fluconazole, itraconazole, voriconazole, posaconazole, multiple tropical formulations

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15
Q

fluconazole

A

highly bioavailable

both oral and IV formulations

highly active against many candida spp

Good: C. albicans, C. tropicalis, C. parapsilosis, C. lusitaniae, C. neoformans, coccidiodes immitis

moderate: candida glabrata (can be susceptible dose-dependent or resistant)
poor: moulds, many dimorphic fungi, candida krusei

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16
Q

AE of fluconazole

A

can cause hepatotoxicity or rash

lower propensity for drug interactions, but still occurs

QT prolongation is possible

eliminated renally, so make sure to adjust dose to renal function. High doses may be required to treat candida glabrata

vulvovaginal candidiasis requires only one dose of 150 mg

17
Q

fluconazole and ICU pts

A

can be used as prophylaxis. if pt has yeast in blood, try echinocandins instead

remember to check pts’s isolate to make sure that candida spp are susceptible

18
Q

itraconazole

A

broader spectrum than fluconazole

Good: in addition to fungi covered by fluconazole, aspergillus spp, many dimorphic fungi

moderate: candida glabrata, candida krusei (can be susceptible dose-dependent, resistant)
poor: zygomycetes, many other moulds

remains drug of choice for some dimorphic fungi like histoplasmosis. Largely replaced by voriconazole in treating aspergillus and other mold infections

Also used to treat Onychomycosis

19
Q

AE of itraconazole

A

in addition to hepatotoxicity, negative inotrope–> don’t give to HF pts

oral solution associated with diarrhea

stronger inhibitor of cytochrome P450, QT prolongation

20
Q

itraconazole formulations

A

capsules–> lower bioavailability than solution and are less preferred for systemic fungal infections

capsules should always be taken with full meals, whereas solutions should be taken on empty stomach

absorption can be lowered by agents reducing gastric acid; have pts take it with soda

absorption is very erratic and unpredictable, so monitor trough concentration during long term treatments

No more IV formulations

21
Q

voriconazole

A

better absorbed than itraconazole and available in both highly bioavailable PO and IV

superior to AmB deoxycholate for invasive aspergillosis and has become drug of choice for that

Good: C. albicans, C. lusitaniae, C. parapsilosis, C. tropicalis, C. Krusei, C. neoformans, Aspergillus spp, many other moulds

moderate: C. glabrata (can be susceptible dose-dependent, or resistant), C. albicans that are fluconazole-resistant, fusarium spp
poor: zygomycetes

22
Q

AE of voriconazole

A

hepatotoxicity, rash, drug interactions, visual effects such as seeing wavy lines or flashing (very common and dose-related), visual hallucination can also occur but less common

check concentration trough on long-term therapy

23
Q

important voriconazole facts

A

active against many fluconazole-resistent strains of candida albicans, but is less active against them than fluconazole susceptible strains. echinocandins is a better choice, but consider a susceptibility testing if need to use voriconazole for an oral options

potent inhibitor and substrate of cytochrome P450, don’t use with rifampin. Cyclosporin (calcineurin inhibitor) requires dose adjustment. many pts who require voriconazole are immunosuppressed

IV form contains cyclodextrin vehicle that accumulates in renal dysfunction–> nephrotoxic–> don’t give to pts with creatinine clearance< 50 mL/min. PO avoids this issue

it’s eliminated hepatically–> not useful in treating candiduria

24
Q

posaconazole

A

currently indicated only for prophylaxis of fungal infections in neutropenic pts and treatment of oropharyngeal candidiasis

Good: C albicans, C lusitaniae, C parapsilosis, C tropicalis, C krusei, aspergillus spp, zygomycetes, many other moulds, dimorphic fungi

Moderate: fusarium spp, candida glabrata (clinical data are lacking for many of them)

25
Q

AE for posaconazole

A

hepatotoxicity, nasuea, rash, drug interactions via cytochrome P450

only available PO and must given with food. high fat food improves absorption (IV for in development)

26
Q

echinocandins

A

caspofungin, micafungin, anidulafungin

inhibit the synthesis of beta-1,3-glucan which is a component of fungal cell wall

Lack of oral administration, but fewer drug interactions than azoles, safer than polyenes, greater activity against fluconazole-resistent yeasts

Good: C albicans, C glabrata, C lusitaniae, C parapsilosis, C tropicalis, C krusei, aspergillus spp

moderate: C parapsilosis, some dimorphic fungi
poor: zygomycetes, most non-aspergillus moulds, C neoformans

27
Q

AE of echinocandins

A

mild histamine-mediated infusion-related reaction, but can be avoided by slowing infusion rate. Hepatotoxicity but not common

28
Q

differences and facts of echinocandins

A

caspofungin and micafungin are eliminated hepatically by non-cytochrome P450 metabolism. anidulafungin degrades in plasma and avoids hepatic metabolism (however it still has hepatotoxic effects)

neither cidal or static effects against aspergillus spp., they cause aberrant, non-functional hyphae to be formed by the actively growing mould

less active against C parapsilosis, consider giving fluconazole instead

don’t use cyclosporine with caspofungin and sirolimus with micafungin

29
Q

echinocandins are good for

A

invasive candidiasis in pts who are unstable. Also in treatment of invasive aspergillosis but not enough supporting data like voriconazole and polyenes.

all of them used for esophageal candidiasis and for prophylaxis for fungal infections in neutropenic pts

Not cheap!

30
Q

ketoconazole

A

poor oral absorption

used topically in treatment of Dandruf

31
Q

Terbinafine (Allyamine antifungal)

A

inhibits squalene epoxidase preventing synthesis of ergosterol

available PO and topically

used for dermatophytes and mainly onychomycosis (concentrates in nails, fat and skin)

metabolized in liver and excreted renally, long half life

AE: hepatotoxicity, neutropenia, steven-johnson syndrome

32
Q

griseofulvin

A

inhibits fungal mitosis via interaction with microtubules

PO, prolonged half-life, active against dermatophytes, mainly headache as AE

33
Q
A
34
Q

fungal drug sites

A

Antibiotics simplified (1 decks)

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