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Pharmacology of Antifungals Flashcards

1
Q

Fungus: Review
Mainly seen as opportunistic or “superinfections”
* Cutaneous infections:
* Systemic infections:

A

common, chronic, seldom dangerous
difficult to diagnose, treat, and often lethal

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2
Q

Visible fungal infection of the mouth can tell you:
(2)

A
  1. Immune status
  2. Drugs they are taking
    ● Daily oral steroids?
    ● Immunosuppressive drugs: transplant?
    ● Antibiotics, Augmentin?
    ● Leukemia, lymphoma?
    ● Chemotherapy drugs – neutropenia?
    ● HIV/AIDS?
    Opportunistic mycoses
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3
Q

Treating Fungal Infections- Selective Toxicity
(2)

A
  • Rigid cell walls
    contain chitin
    and the cell
    membrane
    contains
    ergosterol
  • Selective toxicity
    achieved by
    targeting
    ergosterol
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4
Q

Medically Important Fungal Groups
(3)

A

Molds (Dermatophytes) |
Yeasts (Candida, Cryptococcus, Aspergillus)
 Dermatophytes:

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5
Q

Dermatophytes:
(4)

A

Subgroup of molds that live on skin.
 Normal inhabitants of skin, contagious, spread by contact.
 Produce keratinases that dissolve keratin
 Hyphal filaments penetrate into keratin
 Invades hair shafts & nail beds

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6
Q

►Dermatophyte (Tinea) infections affect

A

keratinized tissues
– skin, nails, hair, etc.

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7
Q

Mold: Dermatophytes
Three common pathogenic dermatophytes:
(3)

A

 Trichophyton Common
 Epidermophyton
 Microsporum

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8
Q

“Tinea” diseases: (“cutaneous mycoses”)
 Tinea capitis –
 Tinea corporis –
 Tinea pedis –
 Tinea cruris –
 Tinea unguium –

A

 Tinea capitis – scalp, common in children
 Tinea corporis – body
 Tinea pedis – athlete’s foot
 Tinea cruris – groin
 Tinea unguium – toenails (onychomycosis)

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9
Q

ALLYLAMINES
(2)

A

»Terbinafine (Lamisil oral or topical)
»Naftifine (Naftin)

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10
Q

ALLYLAMINES
* Binds/inhibits squalene epoxidase
(2)

A
  • Squalene precursors build up and are also
    toxic aiding toxicity
  • Requires actively growing fungi
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11
Q

ALLYLAMINES
* Fungicidal against Dermatophytes Only.
(3)

A
  • Weak fungistatic activity against Candida
  • Little drug interaction potential
  • Few side-effects
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12
Q

Yeast: Candida albicans
Candida:
(2)

A

Most common fungal infection in mouth
» C. albicans normal habitat is the human oral cavity
» propensity to invade and cause disease when an imbalance is created

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13
Q

Oropharyngeal candidiasis (thrush)
 Symptoms: (4)
 Many patients are —
 Immunosuppressed patients with thrush often have concomitant —

A

cottony feeling in the mouth, loss of taste, and/or painful eating and
swallowing.
asymptomatic
Candida esophagitis

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14
Q

Yeast: Candida albicans
Treatment
Oropharyngeal (Tx: 10-days duration)
(3)

A
  • Clotrimazole troches (one 10-mg troche dissolved slowly five times daily)
  • difficult to adhere, poor choice in xerostomia, contains sucrose, DDIs in HIV, taste alterations
  • Miconazole mucoadhesive buccal tabs (50mg 1xdaily apply to mucosal surface
    over canine fossa)
  • Daily dosing, tasteless & sugar free, more expensive, best patient compliance.
  • Nystatin swish and swallow (400,000 to 600,000 units four times daily)
  • not always palatable, contains sucrose, concerning for dental caries over prolonged time periods
  • Good in xerostomia, good in HIV, co-dispense lozenge if has appliances
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15
Q

Yeast: Candida albicans
Treatment
Esophagitis
(1)

A
  • Fluconazole - 400 mg as a loading dose and then 200 to 400 mg daily for 14 to 21
    days given orally
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16
Q

Clotrimazole (Mycelex)
Pro: (1)
Con: (6)

A

Pro:
* Highly effective

Con:
* Ease of use (5x /day)
* Expense
* Drug interactions
possible
* Irritating to mucosa
* Alters taste
* Contains sugar

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17
Q

Miconazole (Oravig)
Pro: (4)
Con: (2)

A

Pro:
* Ease of use (daily
troche)
* Highly effective
* Tasteless
* No sugar

Con:
* Expense
* Drug Interactions
possible

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18
Q

Nystatin
Pro: (3)
Con: (4)

A

Pro:
* No drug interactions
* Inexpensive
* Not irritating to mucosa

Con:
* Ease of use (QID)
* Ease of use (swish contact
time)
* Less effective
* High sugar content

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19
Q

Yeast: Candida albicans
Angular cheilitis (perlèche)
(2)

A

 Acute or chronic inflammation of lateral
commissures
 Caused by excessive moisture and maceration
from saliva

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20
Q

Yeast: Candida albicans
Angular cheilitis (perlèche)
 Treatment:
(2)

A
  • Topical barriers keep moisture out, prevent
    reoccurrences
  • Barrier creams (eg, zinc oxide paste) or
    petrolatum
21
Q

May have Candida superinfection

22
Q

Pharmacology of “Azole’s”
MOA:

A

Inhibit cytochrome P450 14-alpha-demethylase

Fungal cell membrane synthesis
Ergosterol
Azole Antifungal CYP P450 14-alpha-demethylase
Lanosterol

23
Q

First Generation Azoles: Imidazoles

A

Miconazole, Clotrimazole: Not taken systemically
Clotrimazole & miconazole oral formulations less cariogenic; better tolerated vs Nystatin.

24
Q

Miconazole (Oravig): 50 mg (1 tablet) applied to upper gum once daily for
7-14 days

A
  • Apply in morning after brushing. Alternate sides of mouth with each
    application; do not crush, chew, or swallow. Avoid chewing gum while
    in place.
  • If the tablet does not adhere to gum or falls off within 6 hours of
    application, same tablet should be repositioned immediately.
  • Exposure time important: goal entirety of waking hours.
25
First Generation Azoles: Imidazoles Clotrimazole (Mycelex): 10mg (1 troche) dissolved slowly 5 times daily for 7-14 days
* Metabolized in liver – 3A4. Contraindicated in liver disease. * Avoid in combination with benzodiazapines; HIV * Oral Troche for management of oral candidiasis * Patient Education: 5 times daily. Swallow the saliva. No eating or drinking for 30min following medication * Dissolves over 30 minutes and remains in saliva for up to 3 hours
26
Second Generation Azole: Triazoles Fluconazole (Diflucan), itraconazole, voriconazole, posaconazole, isavuconazole
* First line drugs for systemic fungal infections * Fewer drug-drug interactions and expanded spectrum * Still metabolized via the cytochrome P450 enzyme system * All azole agents are both metabolized by and slow down hepatic cytochrome P450 activity * Safer side-effect profiles than ketoconazole for systemic use
27
Second Generation Azole: Triazoles Fluconazole (Diflucan), itraconazole, voriconazole, posaconazole, isavuconazole Dentistry:
Esophogeal candidiasis or refractory, resistant oral candidiasis. Resistance a big problem: 2 Mechanisms- Efflux pumps & altered binding site on demethylase
28
Second Generation Azole: Triazoles Fluconazole (Diflucan) (5)
* High absorption after oral administration with high distribution into all tissues * Long half-life (approx. 24hrs) allows for once-daily dosing * Significant excretion via kidney – dose adjustment when administered to renal impairment * Strong inhibitor of CYP2C19 and a moderate inhibitor of CYP2C9 and CYP3A4 - Caution: benzodiazepines; warfarin * Pregnancy Category C – drug also excreted in breast milk - Avoid in breastfeeding and pregnancy.
29
Fluconazole (Diflucan) Dentistry:
Esophogeal candidiasis or refractory, resistant oral candidiasis. Rx: Fluconazole 200mg tablet, #15 400mg once, then 200mg PO daily x 14days
30
Polyenes Mechanism of Action (4)
* Binds ergosterol in fungal cell membrane * Forms pores in cell membrane * Cell contents leak out * Fungal cell death
31
Polyenes »Binds to ergosterol in fungal membranes. Fungicidal Amphotericin B (Liposomal): Broad spectrum fungicidal for intravenous use (3)
* 1st line IV drug for most systemic yeasts: Histoplasmosis, Aspergillosis, Crypto. * Standard Tx: Cryptococcal meningitis. * Severe, potentially lethal side-effects (dose-dependent nephrotoxicity
32
Polyenes Nystatin (Mycostatin): Broad spectrum fungicidal (4)
* No GI absorption - entirely excreted in feces – Pregnancy Category B (safe) * Topical only for mucocutaneous candidiasis * Length of contact important = 2 MINUTES * Suspension, high sucrose concentration * Alternative to clotrimazole/miconazole
33
Nystatin Patient Counseling: (3)
1. Swish in mouth then, 2. Hold in mouth for as long as possible then, 3. No eating or drinking for 30mins
34
Magic Mouthwash * Common Indications: (3)
* Apthous stomatitis * Recurrent aphthous ulcers (RAU) * Chemo-induced oral mucositis
35
Magic Mouthwash Formula (2)
* NO STANDARD formula * 80% of healthcare facilities compound their own unique formula
36
Magic Mouthwash Ingredients * Most Common: (6)
* Diphenhydramine (Benadryl) >90% * Viscous lidocaine 90% * Magnesium hydroxide/ Aluminum hydroxide (Maalox) 80% * Nystatin 30% * Corticosteroids 10% * Tetracyclines 10%
37
Diphenhydramine (Benadryl) (2)
* Antihistamine / reduce inflammatory process - Limit pain sensation - Reduce swelling, erythema * May be useful for trauma, food allergens, or infections
38
Viscous Lidocaine (3)
* Topical anesthetic * Relieves pain associated with irritated oral/pharyngeal mucous membranes * IMPORTANT: ingesting too much can lead to arrhythmias - Use minimal amounts - Swish and SPIT
39
Magnesium Hydroxide / Aluminum Hydroxide (2)
* Antacid – Maalox and Mylanta * Primarily used as vehicle to enhance coating of other ingredients within the mouth
40
Nystatin (4)
* Fungicidal polyene for mucocutaneous candidiasis * Nonabsorbable by oral route * Not appropriate for RAU or mucositis without fungal etiology * Use if active oral candidiasis infection in concert with RAU or mucositis
41
Corticosteroids (3)
* Hydrocortisone, dexamethasone, betamethasone, beclomethasone * Reduce inflammatory process - Limit pain sensation - Reduce swelling, erythema * Limited evidence for use / controversial
42
Pain/Oral Irritation (3)
* Diphenhydramine - analgesic * Viscous Lidocaine - analgesic * Magnesium hydroxide/ aluminum hydroxide - vehicle * 1-to-1-to-1 ratio * Hx of arrhythmias, atrial fibrillation, etc – may avoid viscous lidocaine * Or 2-1-2 ratio
43
Oral Mucocutaneous Candidiasis * Diphenhydramine - analgesic * Nystatin - antifungal * Magnesium hydroxide/ aluminum hydroxide - vehicle * Corticosteroid – in an opportunistic infection???
NO!
44
Administration (2)
* 2 tablespoons (30mL) every four to six hours * Swish and spit to avoid systemic side effects - Pharyngeal involvement?
45
Side Effects (4)
* taste disturbances (49%) * burning and/or tingling in the oral cavity (29%) * drowsiness or any central nervous system adverse effects (11%) * gastrointestinal symptoms - constipation, diarrhea and nausea (11%)
46
Evidence
The evidence is limited and controversial
47
Controversial because of Formulation Heterogeneity (5)
* Diphenhydramine for all indications * Maalox® for all indications * Lidocaine for pain * Nystatin for candidiasis * Avoid steroids
48

Pharm 2 (13 decks)

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