Background: In regions where there is only itraconazole capsule as a therapeutic option for treatment of chronic pulmonary aspergillosis (CPA), measuring the serum concentrations becomes even more important for therapeutic success.

Objective: Evaluate the initial itraconazole serum trough concentrations after the administration of oral capsule of itraconazole for the treatment of CPA.

Methods: The measurement was performed at least 7-days after initiation of therapy. The standard treatment at our institution was a 200 mg capsule every 12 h. We defined that an adequate serum trough concentration of itraconazole during treatment was 1-4 mg/L.

Results: This study recruited 28 patients. The median value was 0.30 mg/L (IQR 0.01-0.70). Only 11% (n = 3) had adequate serum concentrations based on guideline recommendation. All patients with clinical deterioration had itraconazole serum levels ≤ 0.8 mg/L.

Conclusion: The initial serum concentrations of itraconazole after capsule formulation administration were low. Increasing the dose should be considered when the itraconazole concentration is low, especially if it is ≤ 0.8 mg/L, and the patient presents with clinical deterioration. Larger studies are needed to evaluate the adequate concentrations recommended for CPA.