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Pharmacology Test 3 > Antifungal therapy (Marsella) > Flashcards

Antifungal therapy (Marsella) Flashcards

1
Q

Important drugs

1.

2.

3.

4.

5.

6.

7.

A
  1. Griseofulvin
  2. Amphotericin B
  3. Ketoconazole
  4. Itraconazole
  5. Fluconazole
  6. Terbinafine
  7. Topical therapy
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2
Q

Fungal infections can be

1.

2.

3.

A
  1. Superficial
  2. Subcutaneous
  3. Systemic
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3
Q

Ringworm

A

Dermatophytes

Look for drugs with affinity for the skin

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4
Q

Sporothricosis

(esp cats)

A

Zoonotic

Exudative lesions carry tons of orgs (wear gloves)

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5
Q

Cryptococcus

A

Systemic fungal infection

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6
Q

Griseofulvin

A

Only used rarely

Insoluble in water

Fungistatic

  • Takes a long time to see clinical improvement

Only effective against Dermatophytes

  • Microsporum
  • Epidermophyton
  • Trichophyton
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7
Q

Dermatophytosis

A

Very common in shelter cats (keep zes in bafroom)

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8
Q

Griseofulvin

MOA

A

Primarily active on growing cells

  • Doesn’t work on quiescent organisms

Binds to intracellular microtubules and inhibits

  • Mitosis
  • Synthesis of nucleic acids and proteins
  • Chitin synthesis

Incorporated in keratin

  • but doesn’t bind tightly (gone in a couple days)

​

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9
Q

Griseofulin

Pharmacokinetics

A

Given orally

Absorption

  • variable
  • incomplete
  • dependant on
    • Formulation (ultramicro absorbed better)
    • Food (fatty meals)
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10
Q

Griseofulvin

Metabolism

A

Oxidized by hepatic microsomal enzymes

Excreted in the urine

Metabolism 6 times faster in animals than in people

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11
Q

Griseofulvin

Duration of treatment

A

At least 4 weeks required (up to 3 months or more is normal)

Do not base conclusion of treatment based on appearance: repeat cultures

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12
Q

Griseofulvin

Drug interactions

A

Drug interactions

  • lots of interactions, look up if you prescribe
  • Phenobarb decreases absorption of griseofulvin
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13
Q

Formulations of griseofulvin

A

Microsize

  • Capsules
  • Oral suspension
  • Tablets

Ultramicrosize (more absorbable, less drug required)

  • Tablets
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14
Q

Griseofulvin

Adverse effects

A

GI

  • Bad taste: nausea
  • Vomiting
  • diarrhea

Bone marrow suppression

  • Cats with FIV
  • Breed predilection
    • persians
    • Himalayans
    • Siamese
    • Abyssinians
  • CBC every two weeks

TERATOGENIC

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15
Q

Amphotericin B

about

A

Plyene macrolide AB

Fugistatic/fungicidal

Binds to sterols

  • Fungal and mammalian

Disruption of integrity of cell membrane

  • leakage
  • cellular death

Big gun: Systemic mycoses

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16
Q

Amphotericin B

Spectrum

A

Use for systemic infections

  • Cryptococcosis
  • Blastomycosis
  • Histoplasmosis
  • Coccidiomycosis
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17
Q

Amphotericin

administration

A

Not absorbed orally

Admin IV

  • Dehydration increases toxicity
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18
Q

Amphotericin B

Pharmacokinetics

A

High protein binding

T1/2: 24 hours

Metabolism

  • Tissue sites
  • 10% excreted in urine (organ of toxicity think KIDNEY)
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19
Q

Amphotericin B

Formulations

Dose

A

Liposomal (newer formulations)

  • Better brain penetration
  • can use smaller doses
  • longer half life
  • decreased toxicity

Total cumulative dose

  • given every other day
  • up to 4-8 mg/kg
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20
Q

Amphotericin B

SC

A

Newever formulations can do SC, not idea

  • cheaper
  • still causes some irritation
  • raises total cumulative dose
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21
Q

Amphotericin

Adverse effects

A

Thrombophlebitis

  • Irritating

Nephrotoxic

  • Vasoconstriction
  • Direct toxicity on renal tubules
  • Don’t use with other nephrotoxic drugs
    • stay away from aminoglycosides
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22
Q

Nystatin

A

Yeast infections (common in dog ears)

Binds to ergosterol

Fungicidal/fungistatic

Spectrum of action

  • Candida
  • Malassezia

Topical use

  • poor oral absorption
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23
Q

Azoles

Oral

A

Oral

  • Ketaconazole
  • Itraconazole
  • Fluconazole
  • Voriconazole
24
Q

Azoles

Topical

A

Topical

  • Ketaconazole
  • Miconazole
  • Clortrimazole
  • Thiabendazole
  • Enilconazole
25
Q

Ketoconazole

A

Insoluble in water

Soluble in acidic solution: must give with food

Cidal/static

Inhibition of Lanosterol 14-demethylase

  • Inhibits Ergosterol
  • Affinity for Fungal vs. Mammalian enzyme
  • Suppresses cytochrome P450 enzyme
    • Must decrease doses of cyclosporin
26
Q

Ketaconazole

Spectrum

A

Broad spectrum

  • Systemic infections
  • Dermatophytosis
  • Malassezia
27
Q

Ketaconazole

A

Oral admininistration

Needs acidic environment for absorption: Give with food

Lipophilic

Liver metabolism: need healthy liver

28
Q

Ketaconazole

Therapeutic time frame

A

Delayed therapeutic effect

  • 5-10 days to start seeing effect
  • longer for hair to grow back
29
Q

Ketoconazole

Adverse effects

A

DONT GIVE TO CATS

GI

Hepatotoxicity

  • usually reversible in animals
  • Black box warning for humans

​If anorexic stop Ketoconazole

Teratogenic

Alopecia, pruritis, lightening of coat

Caution in geriatric animals

30
Q

Itraconazole

A

5-100 times more active than ketaconazole

Increased affinity for fungal enzyme

  • fewer adverse effects
  • usually well tolerated in cats

Broad spectrum

Lipophilic

Keratinophilic

31
Q

Itraconazole

A

Liver metabolism

High concentrations reached in skin, adipose tissue

  • poor penetration in CSF, eyes

Longer half life in cats

Tissue levels maintained for a long time

  • suitable for pulse therapy
32
Q

Itraconazole

Administration

A

Oral administration

  • recommended with food
  • avoid antacids
  • liquid solution (10mg/mL)
  • capsules (100mg)

Lower doses for skin problems

Higher doses for systemic infections

33
Q

Itraconazole

Adverse effects

A

Drug interactions

GI upset

Liver toxicity

Vasculitis at high doses

  • vessel injury and necrosis at extremities
34
Q

Fluconazole

A

Newest, most specific, safest

Broad spectrum

Highly specific for fungal enzymes

Good absorption, long half-life

Excellent penetration in the brain

No liver metabolism

Urinary excretion

35
Q

Fluconazole

administration

A

Well tolerated in cats

Prices fluctuate

Now available in generic form

Therapeutic levels persist for 10 days after discontinuation

36
Q

Voriconazole (Vfend)

A

Not used frequently in Vet med

Used in infections in immune compromised patients: Aspergillus

Excellent oral absorption

Liver metabolism

  • P450 suppression: drug interactions
37
Q

Voriconazole

Administration

A

Better tolerated than ketaconazole but more expensive

Adverse effects in humans

  • photophobia
  • blurred vision

Give at same dose in dogs as humans

38
Q

Allylamines

Terbinafine (Lamisil)

About

MOA

A

Primarily

Lipophilic

Keratinophilic

  • persistence in nails for 2-3 months after discontinuation

Mechanism

  • Inhibition of squalene epoxidase
    • inhibition of ergosterol synthesis: highly spec for fungal enzymes
  • ​No suppression of cytochrome P450 (can give with phenobarb)
39
Q

Terbinafine

Spectrum

A

Spectrum: only skin infections

  • Dermatophytosis
  • Malassezia
  • Yeast
40
Q

Terbinafine

Administration

A

Available in tablets, spray, cream

  • animals have too much hair for creams

Well tolerated

Very cheap

41
Q

Iodides

A

Used for Sporotrichosis

  • drug of choice in horses
  • hunting dogs

​Unknown MOA

Cheap

42
Q

Iodides

Adverse effects

A

GI

  • nausea, vomiting, diarrhea
  • give with food

Twitching, hypothermia

Scaling, alopecia

43
Q

Caspofungin (Cancidas)

Echinocandin

A

Pythium: doesn’t have ergostral but has glucan

Glucan synthesis inhibitor

  • specific for fungal walls

Effective against

  • Aspergillus
  • Candida
  • Oomyces: Pythium

IV use

No adverse effects in dogs

44
Q

Ketoconazole shampoo

A

Nizoral, Ketochlor (over the counter)

Expensive

Effective against

  • Dermatophytes
  • Malassezia
45
Q

Chlorhexidine

topical

A

Limited antifungal efficacy

Concentration

  • 2-4%

Frequent treatments

Irritating in some animals

46
Q

Miconazole

Onlyl given topically

A

Leave on conditioner

  • used for Malassezia dermatitis

Available as liquid

  • Conofite
  • Treatment for yeast otitis
  • May cause contact allergy
47
Q

Clotrimazole (lotrimin)

(Only topical)

A

OTC

Spectrum

  • Yeasts and dermatophytes
  • Treatment in ears
  • Don’t do body spot treatments (systemic instead)
48
Q

Enilconazole

A

Can use in environment

  • Dermatophytes survive in environment for up to 2 years

Spectrum

  • Dermatophytes
  • Malassezia
  • Aspergillus

Fungicidal

49
Q

Selenium Disulfide

Selsun blue

A

Kills yeast

Effective against Malassezia

No effect on dermatophytes

Toxic for Cats

Can dry out the skin

50
Q

Lime Sulfur

A

Extremely effective against dermatophytosis

Will stain skin yellow

Will stain tub

Will ruin jewelry

Drying

Sulfur smell

Don’t rinse, must dry on patients

51
Q

Thiabendazole

Tresaderm

A

Antihelpmintic imidazole

Combo product

Malassezia otitis

Ear mites

  • life cycle is three weeks (longer therapy)

Length of therapy

52
Q

Tresaderm

A

Steroid

antibiotic

thiabendazole

  • yeast and mites
53
Q

Clinical case 1

Sam

  • 5 yo, MC, healthy labrador
  • Diagnosed with dermatophytosis
    • Microsporum gypseum in the nail bed
A

Options:

  1. Itraconizole
    * expensive….hundreds of dollars
  2. Terbinafine
  • generic option (cheap)
  • also likes nails
54
Q

Clinical Case

Isabelle

  • 14 yo, FS
  • On cyclosporine therapy for IMHA
  • Diagnosed with generalized Malassezia
A
  1. Ketoconazole
  • old
  • on cyclosporin
  • NOT A GOOD CHOICE

​2. Fluconazole

  • would have to decrease the cyclosporin
    3. Terbinafine
  • Not best choice for yeast
  • Wont have to mess with cyclosporin dose

Also use with a topical shampoo

55
Q

Cyclosporins

A

Cause colitis…? Maybe overdose…

Pharmacology Test 3 (12 decks)

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