Interpretation

A lower cutoff concentration has not been defined that applies in all cases. The serum concentration must be interpreted in association with other variables, such as the nature of the infection, the specific microorganism, and minimal inhibitory concentration results, if available. Localized infections are more likely to respond when serum itraconazole is more than 0.5 mcg/mL (by high-performance liquid chromatography); systemic infections generally require drug concentrations more than 1.0 mcg/mL. Consider target of more than 1.5 mcg/mL for itraconazole plus hydroxyitraconazole. Therapeutic drug monitoring should be done at steady state, which usually occurs in about 7 days. Timing of the serum collection is not as critical due to the drug's long half-life, but trough collections are recommended.