Amphotericin B serum concentrations during therapy.

Therapeutic outcome of patients being treated for systemic mycoses with amphotericin B is possibly related to the serum concentrations of this drug that are produced in these patients. Because current data are conflicting, the magnitude of these concentrations was restudied by using a bioassay which gave precise and accurate results. The highest of 155 serum concentrations was 2.01 mug/ml. Mean concentrations were 1.21, 0.62, and 0.32 mug/ml, at 1, 18, and 42 hr, respectively, after intravenous infusion of amphotericin B. This drug was detected in serum 7 weeks after completion of treatment, but it could not be detected 13 weeks after treatment. Drug levels did not appreciably decrease in serum stored for 8 to 9 months at - 10 C. Unequal serum content in assay tubes and measurement of assay turbidity by visual inspection may explain previously reported amphotericin B levels of 3.0 to 12.5 mug/ml.