All are effective against Tinea versicolor except:
Correct Answer: Griseofulvin
Description: IMIDAZOLES AND TRIAZOLES These are presently the most extensively used antifungal drugs. Four imidazoles are entirely topical, while ketoconazole is used both orally and topically. Two triazoles fluconazole and itraconazole have largely replaced ketoconazole for systemic mycosis because of greater efficacy, longer half life fewer side effects and drug interactions. The imidazoles and triazoles have broadspectrum antifungal activity covering dermatophytes, Candida, other fungi involved in deep mycosis (except mucor), Nocardia, some grampositive and anaerobic bacteria, e.g. Staph. aureus, Strep. faecalis, Bac. fragilis and Leishmania. The mechanism of action of imidazoles and triazoles is the same. They inhibit the fungal cytochrome P450 enzyme &;lanosterol l4--demethylase&; and thus impair ergosterol synthesis leading to a cascade of membrane abnormalities in the fungus. HETEROCYCLIC BENZOFURAN: Griseofulvin: It was one of the early antibiotics extracted from Penicillium griseofulvum. However, because of lack of antibacterial activity, little attention was paid to it: clinical utility in dermatophytosis was demonstrated only around 1960. Griseofulvin is active against most dermatophytes, including Epidermophyton, Trichophyton, Microsporum, etc., but not against Candida and other fungi causing deep mycosis. Bacteria are also insensitive. Dermatophytes actively concentrate it: this feature probably accounts for its selective toxicity. Resistance can be induced in vitro and this is associated with loss of concentrating ability. However, emergence of resistance during clinical use is rare. ESSENTIALS OF MEDICAL PHARMACOLOGY K.D.TRIPATHI SIXTH EDITION PAGE NO:760,761
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