Limits of antifungal prophylaxis by ketoconazole in leukemic patients

Serum ketoconazole levels in leukemic patients, subjected to ketoconazole prophylaxis, were determined by an agar diffusion assay. High individual variability of drug concentration was noted. In addition, the highest drug concentration observed was less than 1 microgram/ml in 5 out of 6 patients studied. The reliability of prophylaxis of airborne opportunistic fungal infections by ketoconazole seems, therefore, to be hampered, at least in leukemics, by the too low serum concentrations of the drug. The bioassay proved to be highly reproducible and accurate as well as easy and safe to perform.