Antifungals Flashcards
What are the modes of action of anti fungals?
*bind to egosterol (fungi cell membranes), altering permeability, leakage of ions and transport- death. Eg Nystatin, amphotericin
*inhibition of ergosterol synthesis- inhibit essential cytochrome P450 step, inhibits conversion of lanosterol to ergosterol. Leads to accumulation of sterols- altered cell membrane function - Azoles (imidazoles, triazoles)
*effect proteins needed for polysaccharide in cell walls- capsofungin
*inhibition of protein and DNA synthesis- flucytosine
How is amphotericin administered usually and why?
IV or in lipid formulations (liposomal amphotericin B) due to being poorly absorbed by gut
What is a major side effect of amphotericin?
Nephrotoxicity- monitor renal function
How do azoles function?
Imidazoles and Triazoles
*inhibit ergosterol synthesis- inhibit cytochrome p450 step- lanosterol not converted to ergosterol
*sterol accumulation- lead to cell membrane with altered function
What are examples of imidazoles?
*clotrimazole
*miconazole
*ketoconazole- better oral absorption- hepatotoxicity
Topical
What are examples of triazoles?
*fluconazole- oral
*itraconazole- C/I in liver disease
When is capsofungin used?
For aspergillosis
When is terbinafine used?
Fungal nail infections- decreases ergosterol synthesis
How are fungal diseases caused?
*mycotoxicoses- accidental/deliberate ingestion of fungi that produce mycotoxins
*hypersensitivies- pneumonitis
*colonisation- superficial, cutaneous, subcutaneous and systemic
What is superficial mycoses?
*colonisation of outermost layers of skin and hair shaft
*no immune response
*treat by improving hygiene
What is cutaneous mycoses?
*keratinised layers of skin
*immune response
*skin (ringworm) , hair , nails
*treat with imidazoles- clotrimazole, miconazole- topical
*oral- terbinafine
