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AntiFungals Flashcards

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1
Q

___ are resistant to most ABX

A

Mycobacteria

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2
Q

Mycolic acids and associated compounds form a ___

A

waxy coat around the organism

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3
Q

Antitubercular Drugs used in ___

A

combination

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4
Q

Primary AntiTB drugs:

A

Isoniazid
Ethambutol
Pyrazinamide
Rifamycins (Rifampin)

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5
Q

Isoniazid

A

most effect anti TB drug
only effective against mycobacteria
Prodrug metabolized by mycobacteria to its active form
MOA: Inhibition of mycolic acid biosynthesis
Wide distribution (enters cells, CSF)
Tx and prophylaxis

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6
Q

Isoniazid Metabolism

A

Acetylation by NAT-2 (highly polymorphic)

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7
Q

Isoniazid Adverse Effects

A 
Usually well-tolerated
rash, fever
Seizures in pts w/disorders
Mild hepatotoxicity
*** Dose dependent Peripheral neuropathy (pseudo deficiency of Pyridoxine/B6 so its always given with isoniazid)
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8
Q

Rifamycin MOA

A

MOA: High affinity for bacterial DNA-dependent RNA polymerase (inhibits DNA transcription)

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9
Q

Rifamycin

A

broad spectrum
bacteriostatic
rapid resistance (used only in combo therapy)
RIFAMPIN

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10
Q

Rifampin

A 
well absorbed PO
Wide distribution
ext enterohepatic circulation
De acetylated in liver; active metabolites
3-% excreted in urine
urine - red/orange
may color other excretions
"Red man syndrome"
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11
Q

Rifampin Adverse Effects

A 
well tolerated for most
rash, fever, N/V
Maybe hepatotoxic
Powerful inducer for CYP3A4
Significant drug interaction
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12
Q

Rifabutin

Rifapentine

A

TB tx in HIV patients; rifampin resistant organisms

long T1/2
rifampin resistant organisms

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13
Q

Ethambutol

A

Only active against mycobacteria (inhibits an enzyme involved in mycobacterial cell wall biosynthesis)
rapid resistance (not used alone)
Excreted in urine

can cause red/green color blindness and interferes with uric acid excretion - Gout

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14
Q

Pyrazinamide

A

only effective against mycobacteria
inhibits synthesis of mycolic acids
bactericidal at acidic pH
Well absorbed and wide distribution
parent drug and metabolites excreted in urine
can be hepatotoxic, inhibits uric acid secretion - gout

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15
Q

TB Treatment

A

prophylaxis - isonazid 12 months

Initial tx
Induction phase - isoniazid,/pyridoxine, rifampin, ethambutol, pyrazinamide for 2 months
Consolidation Phase - continue isoniazid/pyridoxine, rifampin for at least 4 months

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16
Q

Multiple Drug resistant -

Extensively drug resistant

A

MDR - isoniazid and rifampin

XDR - isoniazid, rifampin, and fluoroquinolones and at least one second line drug

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17
Q

Mycobacterium avium complex (MAC)

A

Immunocompromised patients

Abx - rifabutin, Azi-, or clarithromycin

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18
Q

Mycobacterium Leprae

A

Leprosy (Hansen’s)
tropical areas
Abx - dapsone, clofazimine

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19
Q

Fungi are __ and rarely

A

eukaryotic and rarely cause invasive infections except in immunocompromised

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20
Q

Yeast

A

Round, free living
Candida - MC

Thrush - infants and immunocompromised

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21
Q

Molds

A

Filamentous
Aspergillus - MC
Less susceptible to chemo

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22
Q

Dimorphic

A

Can grow as yeast or mold

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23
Q

Common Yeasts

A

Candida, cryptococcus

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24
Q

Common Molds

A

Aaspergillus, mucorales, Rhizopus, Dermatophytes

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25
Common Dimorphic
Blastomyces, Coccidioides (Desert Fever), Histoplams, Sporothrix
26
4 MOA of antifungals
1. Disrupt cell membranes - target Ergosterol 2. Inhibit cell wall synthesis 3. Inhibit nucleic acid synthesis 4. Impair microtubules in mitotic spindle
27
Drugs that disrupt cell membranes
Polyenes, azoles, allylamines, benzylamines
28
Drugs that inhibit cell wall synthesis
Echinocandins
29
Drugs that inhibit nucleic acid synthesis
Flucytosine
30
Drugs that impair microtubules in mitotic spindle
Griseofulvin
31
Almost all antifungals are effective against
Yeast
32
Amphotericin B
``` Polyene Antifungal lipophilic Long half-life given IV (qD) Forms colloidal suspension ```
33
Amphotericin B MOA
``` Binds ergosterol with high affinity ampho/ergo complex aggregates and forms pores in membrane - detergent action Fungicidal concentration dependent killing Broad spectrum Resistance is rare ```
34
Amphotericin B Adverse Rxn
rigor, fever, chills, hypotension (histamine, TNF-Alpha, IL-1) - so slow infusions, give NSAIDS, glucocorticoids Nephrotoxic - saline loading Anemia - decreased erythropoietin
35
Amphotericin B Lipid-Based
Liposomal Amphotericin B - Lowest incidience of nephrotoxicity and infusion reactions Very expensive!
36
Amphotericin B PK
Polyenes are non-absorbed from GI slow clearance - non renal, non hepatic plasma protein bound Little penetration to CSF
37
Topical Polyene
Nystatin, natamycin, Amph B Topicals
38
Azole Antifungals
inhibits ergosterol biosynthesis (lanesterol demthylase - fungal CYP 450) = cell death Imidazoles, triazoles
39
Azole Antifungals Activity
All are effective against common yeast (candida, cryptococcus) Triazoles have broader antifungal activity (active for aspergillus and other molds)
40
Azole Antifungals PK
Orally effective some need acidic pH some need to be taken with meals, some don't. Some can be taken IV All azoles are metabolized by CYP enzymes (drug interactions with antacids and PPIs and hepatotoxic) variable half life
41
Ketoconazole
Azole poor oral absorption - needs acidic pH Gynecomastia, mentrual probs, hepatoxic, Has been used for Cushings
42
Fluconazole
``` 100% oral Bioavailability Penetrates CSF Used for crypto Meningitis Renal elimination Inhibits CYPs Best tolerated of Azoles Oral - oropharyngeal candida single dose for vaginal yeast Narrowest Spectrum Resistance is becoming commonItraconazole ```
43
Itraconazole
Triazole Aspergillus Drug of choice for dimorphic - blastomycosis
44
Voriconazole
``` Broad spectrum Drug of Choice for aspergillus - better than Amphotericin B (not good for mucorales) Variable Blood levels Good oral absorption Available in IV Toxic - visual disturbance, Class D ```
45
Azoles Adverse Rxns
``` Hepatotoxic Drug interactions (CYP 450) Decreased steroid hormone biosynthesis (adrenals, testes, ovaries) Prolonged QT interval ```
46
Echinocandins
``` Caspofungin Inhibits Beta-D-glucan biosynthesis (part of cell walls) Fungicidal Common yeasts and aspergillus Dimorphic do not respond reliably ```
47
Echinocandins PK
Not absorbed after oral admin IV once/day very protein bound, poor CSF levels. Slow clearance - hydrolysis, and fecal elimination
48
Echinocandins Adverse Effects
selective targeting of fungal cell wall (selective toxicity) Well tolerated histamine like infusion reactions with rapid admin altered LFT
49
Flucytosine
Selective toxicity - interacts with cytosine specific permeases and cytosine deaminase converts to active metabolite - 5-Fluorouracil Rapid resistance - not used alone
50
Flucytosine Properties
Orally effective Used in combo with Ampho-B Adverse -GI, bone marrow suppression, hepatotoxic Renal elimination
51
Squalene Epoxidase Inhibitors
Allylamines - Terbinifine*** Early step in ergosterol biosynthesis (lack of which messes with fungal membrane function) Only effective against dermatophytes Available in topical
52
Terbinifine
deposited in skin and nails - low levels in blood Oral admin - effective Treatment for onychomycosis
53
Terbinifine
well tolerated GI, HA, bad taste long term admin is required CYP2D6, some hepatotoxicity
54
Griseofulvin
Made from PCN MOA = inhibits mitotic spindle formation and cell division Fungistatic Only good for superficial skin and nail infections
55
Tinea Capitis
Griseofulvin (better for kids) Terbinifine (more effective, but more expensive and more adverse effects)
56
Griseofulvin
Oral admin Better absorption with microsize formulation Deposited in keratin precursor cells (prevents fungi invasion, outer layer sloughed off and terminates infection) Minor Adverse Rxns - Headache is MC Leukopenia
57
MOAs Membrane function: ____ Ergosterol Synthesis: ____ Cell wall synthesis:_____ Nucleic Acid Synthesis:____
Membrane function: Ampho B Ergosterol Synthesis: Fluconazole, voriconazole, Terbinifine Cell wall synthesis: Caspofungin Nucleic Acid Synthesis: 5-Fluoroqionolone
58
Summary | Ampho B
Broad Spectrum Must be IV Significant toxicity
59
Summary | Azoles
Triazoles Oral Less serious adverse Rxns
60
Summary | Echinocandins
Yeast and aspergillus | IV
61
Summary Narrow Spectrum (yeasts)
Fluconazole
62
Summary Adds aspergillus and other molds
Ampho B Voriconazole Caspofungin
63
Summary Activity Agianst Dimorphic
Ampho B

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