Mechanisms of action of the antimycotic imidazoles

The mechanism of the antifungal action of the imidazole antimycotics, miconazole ano clotrimazole, on Saccharomyces cerevisiae was explored. When grown aerobically both drugs were fungistatic at low concentrations and fungicidal at high concentrations. When grown anaerobically the fungistatic effect was not seen, but killing still occurred at high concentrations. The fungistatic effect correlated with inhibition of ergosterol synthesis and elevated lanosterol/ergosterol ratios in the organisms. The fungicidal effect involved rapid membrane damage and was unrelated to the imidazole-induced block in ergosterol synthesis. These agents each have 2 distinct antifungal actions.