Antifungal agents Pawitra Pulbutr M.Sc. In Pharm (Pharmacology) วัตถุประสงค์เชิงพฤติกรรม • เข้าใจและอธิบายถึงกลไกการออกฤทธิ์, การดื้อยา, เภสัชจลนศาสตร์, อาการไม่ พึงประสงค์ท่เี กิดจากการใช้ยา, การนาไปใช้ประโยชน์ทางคลินิก รวมทัง้ ข้อดี และข้อเสียของยาต้านเชื้อรา Antifungal agents Systemic antifungal for systemic infection Systemic antifungal for mucocutaneous infection Topical antifungal agents Systemic antifungal for systemic infection • Amphotericin B • Flucytosine (5-FC) • Azoles • Ketoconazole • Itraconazole • Fluconazole • Voriconazole Amphotericin B Mechanism of action Cell membrane binding Target = Ergosterol of fungal cell membrane Pore forming action Increase cell membrane permeability Selective fungicidal Resistance Decrease ergosterol binding decrease ergosterol number decrease ergosterol affinity Antifungal activity • Most broadest spectrum • Candida albicans • Cryptococcus neoformans • Histoplasma capsulatum • Blastomyces dermatitidis • Coccidioides immitis • Aspergillus fumigatus • Paracoccidioides brasilliensis • Penicillium maeneffei • Mucormycosis (Rhizopus, Rhizomucor, Cunninghamella) • Not to … Candida lusitaniae, Pseudallescheria boydii ADRs • Immediate reaction • Infusion related toxicity • Fever, chills, muscle spasms, vomiting, headache, hypotension • Slower infusion • Premedication with ibuprofen, paracetamol, diphenhydramine, hydrocortisone ADRs • Slower reaction – Drug toxicity – Renal damage • decrease renal perfusion, prerenal failure … reversible • renal tubular injury, tubular dysfunction … irreversible • renal tubular acidosis, severe Mg++ & K+ wasting >>> hypokalemia – Sodium loading >>> decrease prerenal toxic Amphotericin B formulation • Conventional • Amphotericin B desoxycholate (DOC) • Lipid formulation •Amphotericin B Colloidal Dispersion (ABCD) •Amphotericin B Lipid complex (ABLC) •Small unilamellar vesicle formulation of amphotericin B (AmBisome®) Less bind to mammalian cells… Less nephrotoxicity Expensive Flucytosine (5-FC) water soluble pyrimidine analog 5-FU like structure Well GI absorption > 90% Well distribution … including CSF Renal excretion … glomerular filtration … Mechanism of action Uptake into fungi by cytosine permease Converted into 5-FU … converted to … 5-fluorodeoxyuridine monophosphate (F-dUMP) … inhibit DNA synthesis 5-fluorouridine triphosphate … inh. RNA syn. Azole compounds • Imidazole • ketoconazole • miconazole • clotrimazole • Triazole • itraconazole • fluconazole • voriconazole Mechanism of action • Inhibit fungal CYP 450 • sterol 14 α demethylase • Inhibit ergosterol synthesis • Imidazole … less specific to fungal enzyme • Imidazole … may inhibit human enzyme … • Drug interaction … Enzyme inhibitor • ADRs… Inhibit steroid hormone synthesis Clinical uses Broad spectrum Candiasis Cryptococcosis Blastomycosis Histoplasmosis Dermatophytosis … ringworm Pseudallescheria boydii infection Aspergillosis Sporothricosis Systemic drug for mucocutaneous infection Griseofulvin Terbinafine Griseofulvin • • • • • • • Unclear mechanism of action … fungistatic – inhibit mitotic spindle function … Inhibit fungal mitosis Accumulation in keratin New skin … Non-infected Oral … well absorption with fatty meal Skin/ Nail/ Hair fungal infection Late onset… 2-6 week Microsized & Ultramicrosized preparation Terbinafine (Lamisil®) Synthetic allyamine … well oral absorption … extensive first pass metabolism Mechanism … Inhibit ergosterol synthesis Inhibit fungal squalene epoxidase Accumulation of toxic sterol squalene Fungicidal & Keratophilic Clinical uses Dermatophytes Onychomycosis 250 mg/ day 6 weeks (finger) or 12 weeks (toe) Topical antifungal therapy • Superficial & Cutaneous fungal infection • Stratum corneum, Squamous mucosa, Cornea • Dermatophytosis (ring worm) • Cutaneous candidiasis • Tinea vesicolor, Piedra • Fungal keratitis • Not effective for onychomycosis, tinea capitis (head), subcutaneous mycosis Nystatin New York State Health Lab Polyene macrolide Pore forming at cell membrane Amphotericin B like mechanism Topical only for candidiasis only Non GI, mucus absorption Clinical uses … local candida infection Oral suspension / Vaginal tablet Oral thrush (swish & swallow), Vaginal candidiasis, Intertriginous candidal infection Topical Azole • Clotrimazole • Cutaneous application • Miconazole • Econazole • Isoconazole • Ketoconazole • Vaginal suppository (Clotrimazole) • Oral troches • Tinea corporis, Tinea pedis, Tinea crusis • Vaginal candidiasis, Oral thrush, Cutaneous candidiasis • Seborrheic dermatitis • Pityriasis vesicolor Topical allylamine Terbinafine Naftifine Tinea crusis, Tinea corposis, Tinea pedis Less effective to Candida*, tinea vesicolor* Irritation Systemic antifungal for systemic infection Amphotericin B 5-FC Azole .. Ketoconazole, itraconazole, fluconazole, voriconazole Systemic antifungal for mucocutaneous infection Griseofulvin Terbinafine Topical antifungal agents Nystatin Topical azole Topical allylamine Miscellaneous