Kays Antifungal Agents Lecture 1 Flashcards
What are the common Candida species
C. albicans, C. glabrata, C. parapsilosis, C. tropicalis, C. krusei, C. guilliermondii, C.
lusitaniae, C. auris (multidrug-resistant)
Invasive candidiasis refers to
to severe forms of the disease (not oropharyngeal or
esophageal candidiasis or uncomplicated candiduria
Risk factors for invasive candidiasis:
prolonged stay in ICU; central venous catheters;
prolonged therapy with broad spectrum antibacterial agents; receipt of parenteral
nutrition; recent surgery (especially abdominal); hemodialysis; diabetes mellitus
Aspergillus species is what type of species
mold that is ubiquitous in the environment
Aspergilluses causes infections primarily in
immunocompromised hosts (neutropenia) and it is difficult to treat
Cryptococcus neoformans is an
Encapsulated yeast that primarily affects the CNS and respiratory tract
Cryptococcus neoformans is most common in patients with
HIV, who have received organ
transplants, or high-dose corticosteroid
Zygomycetes pathogen types are
Rhizopus, Absidia, Mucor
Zygomycetes infections are common in what areas of the body
pulmonary system; paranasal sinuses with extension to the brain
Primary risk factors for Zygomycetes are:
diabetes mellitus
immunosuppression (with profound neutropenia)
penetrating injuries from natural disasters (tornadoes, hurricanes, volcanic eruptions) or combat
Histoplasma capsulatum is most common in what area of the united States
Midwestern states along Ohio and Mississippi river
valleys; exposure to bat guano (cave exploration) or other large birds; demolition or
construction
Blastomyces species is most common in whats area of the united states
Southeastern and Midwestern states along Ohio and
Mississippi river valleys and Great Lakes region
Coccidioides immitis/posadasii is most common in what area of the United States
cluster in southwestern United States (southern
Arizona, southern California, southwest New Mexico, west Texas)
Ampotericin B MOA
Increases membrane permeability of fungal cells by binding to ergosterol and causes leakiness and loss of membrane potential
Amphotericin B Resistance MOA & Pharmacodynamic monitoring parameter
- decreased ergosterol biosynthesis, synthesis of alternative sterols.
Monitoring Parameters is Peak to MIC ratio
Amphotericin B Spectrum of activity
- Candida species (not C. lusitaniae)
- Cryptococcus neoformans
- Blastomyces dermatitidis
- Histoplasma capsulatum
- Coccidioides immitis
- Aspergillus species (reduced activity against A. terreus)
- Mucor species (and other zygomycetes)
Deoxycholate distribution ) used with amphotericine
Poor penetration into CSF, even if meninges are inflamed (»3% of serum)
Highly protein bound (> 90%) – mainly to b-lipoproteins
not appreciably metabolized
Deoxycholate elimination
Tri-exponential elimination. 1/2 life 24-48 hours and terminal elimination in 15 days. Renal and Hepatic impairment do not affect clearance
Lipid associated formulations of amphotericin B an kidney concentrations
80-90% reduction of concentrations in the kidneys
Clinical Uses of Deoxycholate
- Disseminated candidiasis
- Cryptococcosis
- Aspergillosis
- Histoplasmosis
- Blastomycosis
- Coccidioidomycosis
- Mucormycosis
Deoxycholate Dosing and Administration
0.1mg/kg or 1kg over 20 to 30 minutes (do not premedicate.
Infused over 4-6 hours (rapid infusions associated with more adverse reactions.
Intrathecal/ intraventricular administration: 0.1mg then increase to a maximum o f0.5 every 48-72 Hours
L-AmB dosing
1.5-6mg/kg daily infused over 2 hours
ABLC Dosing
5mg/kg dosing daily, infused at 2.5mg/kg/hour
Dosing Weight for Amphotericin B
Use Ideal or adjusted despite lipophilicity
Deoxycholate infusion related Adverse reactions
- Infusion related (pretreat with NSAID, antihistamine etc)
- Thrombophlebitis: slow infusion and rotate sites, consider adding heparin
Deoxycholate Non-infusion related adverse reactions
- Dose dependent nephrotoxicity (increases in serum creatinine and BUN) can consider sodium repletion in depleted patients. use saline both before and after AMB
- Hypokalemia, Hypomagnesemia, Bicarb wasting, anemia
Intrathecal Deoxycholate administration adverse effects
nerve pain, head ache, vomiting, paraplegia, seizures,
Lipid associated formulations of amphotericin B an there adverse effects
Less nephrotoxicity & infusion-related toxicities with lipid-associated formulations except for ABCD.
- manage L-AMB infusion reactions with diphenhydramine
Interactions for Amphotericin B
- Nephrotoxic agents
- Digoxin and skeletal muscle relaxants, may potentiate hypokalemia
- Flucytosine - increase therapeutic effect and increase potential toxicity
FLUCYTOSINE Mechanism of Action
- 5-FC enters fungal cell –> deaminated to 5-FU –> 5-FU gets incorporated into fungal
RNA –> interference with protein synthesis - 5-FC enters fungal cell –> metabolized to 5-fluorodeoxyuridine monophosphate –>
inhibits thymidylate synthetase –> interferes with DNA synthesis
FLUCYTOSINE Spectrum of activity
- Cryptococcus neoformans
2. Candida species
FLUCYTOSINE PK
- Absorption – well absorbed orally (> 90%
- Distribution
a. Penetrates into CSF ( »75% of serum)
b. Negligible protein binding (2 to 4%) - Metabolism/Excretion
a. Small amount converted to 5-FU
b. 85 to 95% excreted unchanged in urine
c. Normal half-life – 3 to 5 hours; anephric half-life – 85 hours
d. Removed by HD & PD
Flucytosine clinical use
primarily in combination with amphotericin B for cryptococcal meningitis
Flucytosine Adverse reactions
- Gastrointestinal (6%) – nausea, vomiting, diarrhea, abdominal pain, enterocolitis
- Hematologic – Bone marrow suppression (more common with serum concentrations > 100 μg/ml)
Flucytosine Dosing
Normal Renal Function – 100 to 150 mg/kg/DAY PO in 4 divided doses (25 to 37.5 mg/kg/DOSE Q6H) – available in 250 mg and 500 mg capsules.
Renal Dosing
see chart start at 25-37.5 when greater than 40 q 6 hours
Dosing body weight for Flucytosine
ideal body weightfor non-severe
adjusted body weight if severe
Flucytosine Monitoring
a. Baseline: CBC, platelets, Scr, BUN
b. Reduce dose in patients with bone marrow or GI toxicity
Ketoconazole MOA
- inhibits synthesis of ergosterol via inhibition of the fungal cytochrome P-450 dependent
enzyme lanosterol 14-α-demethylase - Blocks formation of ergosterol → damage to fungal cell membrane –> disruption of
structural integrity –> leakage of cytoplasm –> inhibition of growth (fungistatic)
Ketoconazole Spectrum of Activity
- Candida albicans
- Cryptococcus neoformans
- Histoplasma capsulatum
- Dermatophytes (tinea
Ketoconazole PK
Absorption
a. Well absorbed orally (F=75%); peak concentration 1 to 2 hours after oral dosing
b. Absorption is inversely related to gastric pH
Distribution
a. Widely distributed throughout body (CSF penetration is negligible)
b. Protein binding 95 to 99%
Metabolism/Elimination
a. Extensively metabolized in the liver
b. Major excretory route is enterohepatic – 85 to 90% excreted in bile & feces
c. Biphasic elimination – half-life 2 hours (during the first 8-12 hours); 9 hours
thereafter
d. Dosage adjustment not needed in renal failure; not removed by HD or PD