The action of itraconazole and ketoconazole on growth and sterol synthesis in Aspergillus fumigatus and Aspergillus niger.

Growth and sterol synthesis of Aspergillus fumigatus and A. niger were studied in control cultures and in the presence of ketoconazole or itraconazole, the latter compound being 100 times more growth inhibitory than the former. Sterol synthesis is inhibited more rapidly than any visible fungal outgrowth. This inhibition results in an accumulation of 4,14 dimethyl- and 4,4',14 trimethylsterols. The presence of these membrane-disturbing sterols may result in a pertubation of membrane-bound enzyme systems such as chitin synthase.