Toxicodynamics of itraconazole: implications for therapeutic drug monitoring.

We explored concentration-toxicity relationships for itraconazole among 216 patients. Logistic regression revealed a progressive increase in the probability of toxicity with increasing concentrations of itraconazole. Classification and regression tree analysis suggested that 17.1 mg/L of itraconazole (measured using a bioassay) was the concentration level at which the population of patients was separated into 2 groups, each with a high and a low probability of toxicity.