Itraconazole vs amphotericin B: in vitro comparative evaluation of the minimal inhibitory concentration (MIC) against clinically isolated yeasts

Itraconazole is a triazole compound which, following several clinical trials, has begun to be used for therapy of mycotic infections. This new drug, with a broad-spectrum antifungal activity, can be orally administered. The Authors studied the in vitro susceptibility to amphotericin B and itraconazole of the following clinical isolates of pathogenic yeasts: 100 Candida albicans, 20 C. tropicalis, 20 C. parapsilosis, 8 C. guilliermondii, 6 C. pseudotropicalis, 24 Torulopsis glabrata and 16 Cryptococcus neoformans. Serial two-fold dilutions, from 100 μg/ml to 0.04 μg/ml, of each drug were prepared in Yeast Nitrogen Base + Glucose 5%, after dissolving the itraconazole in dimethylsulfoxide (DMSO) and amphotericin B in 5% glucose solution. Amphotericin B (MIC₉₀: 3.12 μg/ml) was found to have an average in vitro MIC six-fold lower than itraconazole (MIC₉₀: 25 μg/ml). Thus, even though itraconazole is active, amphotericin B remains one of the most effective of the antifungal drugs.