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13 Cards in this Set
- Front
- Back
Antifungals.
Name 9 antifungals and the general mode of action. |
• Like bacteria, have both a cell wall and a cell membrane
• Many antifungals target the predominant fungal cell membrane steroid, ergosterol Amphotericin B Nystatin Clotrimazole Miconazole Ketoconazole Fluconazole Itraconazole Terbinafine Griseofulvin – structurally different to the main animal cell membrane steroid, cholesterol |
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Amphotericin B.
MOA. What are the 3 things it treats. 2 points and 1 side effect. |
MOA:
1.Amphotericin B traverses the fungal cell wall and reaches cell membrane 2.Intercalates to cell membrane via ergosterol binding 3.Increases cell membrane permeability resulting in cell electrolyte leakage dose-dependent fungicidal Preferentially binds to ergosterol (rather than cholesterol) to provide fungal selectivity! Treats Aspergillus, Cryptococcus, Candida. Poor GIT absorption but still given PO, IV/SC Side Effects : Nephrotoxicity : extension of the mechanism of action acting on renal tubular cell cholesterol, renal vasoconstriction. Effects are cumulative. |
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Nystatin
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MOA: as above.
For ear medication Little systemic absorption there fore safe! |
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Azoles. MOA
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MOA: Azole inhibiting sterol synthesis leads to creation of defective steroid. Defective steroids disrupt cell membrane integrity =Fungistatic
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Clotrimazole
(Topical ) |
Cannot be given systemically. Increased metabolism results in subsequent doses not reaching therapeutic concentrations
• Used topically ie infused through a nasal catheter to treat nasal aspergillus |
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Miconazole
(Topical) 3 diseases 2 points. |
“Malaseb” Miconazole, Chlorhexidine. Used for
Ringworm Staphylococcus intermedius Malassezia pachydermatis Ear medications Very little systemic absorption, so minimal side effects. |
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Ketoconazole. 3 side effects.
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Only absorbed from acid environment (pH <3), therefore give PO after meal
GIT side effects (vomiting) Hormonal side effects (can inhibit progesterone >conversion). Gynecomastia, impotence, hypocortisolemia • Inhibits HME, used to decrease cyclosporin dose Hepatic side effects esp cats |
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Fluconazole
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Much better oral absorption and efficacy & less side effects than ketoconazole
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Itraconazole
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Requires an acid environment for oral absorption.
Improved efficacy and less side effects than ketoconazole |
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Terbinafine. MOA.
2 pharmacokinetics and what does it treat? |
Highly fungicidal
• Mechanism of action conceptually similar to the azoles Good oral absorption • Broad spectrum - ringworm, Cryptococcus, Candida, Aspergillus, Malassezia Good distribution - lipophilic. Stratum corneum concentration is 75 times that of plasma |
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Griseofulvin. 2 side effects what does it treat? MOA
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MOA: inhibits assembly of microtubules & disrupts mitotic spindle> mitotic arrest (fungistatic)
– limited immunological clearance of keratin based infection Very lipophilic – Oral meds should be given with fatty meals – Concentrates in the keratin layers (skin, hair, nails) Good distribution for targeting a superficial fungal dermatitis • binds tenaciously to keratin so DOA >> t1/2 (dog - 47mins) Fungistatic + binds to keratin layer – relies on skin/hair/nails to “grow out” or desquam before “clean” keratin is seen Fungal cells preferentially take up the drug (cf. mammalian cells) Efficacy against ringworm but therapy may last weeks . Side Effects Teratogenicity=avoid in pregnant animals Cats especially sensitive: CNS, anaemia, neutropenia (decreased neutrophils), liver toxicity |
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Copper Sulfate, Pool Chlorine & Povodine Iodine
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Cheap topical biocidal therapies used in production animals for keratomycoses
Especially show cattle |
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Antivirals
(Acyclovir, Famciclovir) |
MOA acyclovir : a defective GTP that is incorporated into the viral genome and terminates DNA synthesis. > > Topical use only.
Famciclovir :Encouraging in vivo results coming through for treating feline herpesvirus in the eye |