Imidazole antifungals

Group of antimycotics that inhibit the ergosterol synthesis of fungal cells. This leads to a fungistatic effect. The characteristic feature of azoles is the five-membered heterocyclic ring, with 2 nitrogen atoms, which is complexly substituted.

The various imidazoles differ significantly in their chemical structure and biological effectiveness. The following imidazole antimycotics:

• Clotrimazole
• Bifonazole
• Miconazole
• Ketoconazole
• Oxiconalzol
• Sertaconanazol
• Tioconazole

The microsomal enzyme lanosterol demethylase, a cytochrome P450 isoenzyme of fungi, which catalyses the synthesis of ergosterol from other steroid precursors, is specifically inhibited. Inhibition of the cytochrome P450 isoenzyme leads to a deficiency of this essential building block of the cytoplasmic membrane and thus to massive disruption of membrane function, which gradually disrupts growth and increases vulnerability to external influences (fungistatic effect). The subsequent accumulation of toxic precursors of ergosterol in the fungal cell causes irreversible damage to the cell, which dies after some time. With low potency azole antifungals also inhibit human cyp-enzymes. Ketoconazole also inhibits the synthesis of testosterone. Ketoconazole has hepatotoxic effects.

Dermatophytes, Candida species, yeast fungi of the genus Malassezia furfur.

Due to the various side effects, azoles are nowadays only used topically in concentrations of 1-2%. The absorption through the skin is < 1% of the applied amount. In the intertriginous area azole-containing pastes are particularly suitable for application. The absorption of azoles through the mucous membrane (e.g. in candida vaginitis) is 3-10% of the applied dose.

Dermatophytosis, candida infections of skin and mucous membranes, pityriasis versicolor; seborrheic dermatitis

A number of azole antifungals are no longer subject to prescription and dmait is no longer available on prescription at the expense of health insurance companies.

1. Farm W: General mycology. In: Dual series, Medical Microbiology. 7th edition. Thieme publishing house Stuttgart S 483