Abstract
PURPOSE: Posaconazole plasma levels can vary considerably among patients, underscoring the need for therapeutic drug monitoring (TDM). Nevertheless, access to TDM is limited in many clinical settings. This study aimed to investigate the impact of posaconazole TDM in daily practice at a tertiary care hospital. METHODS: We conducted a single-center retrospective study at a university hospital, reviewing patients who received posaconazole delayed-release tablets and underwent TDM between January 1, 2022, and December 18, 2023. RESULTS: A total of 35 patients with 74 posaconazole TDM were evaluated. Twenty-seven (77.1%) patients received posaconazole for prophylaxis. The median plasma concentration of posaconazole was 1.45 mg/L (interquartile range [IQR]: 1.74 mg/L). Overall, 74.3% of posaconazole concentrations were within the target range. Target attainment was achieved in 75.9% of prophylactic measurements (> 0.7 mg/L) and 68.7% of treatment measurements (> 1 mg/L). Subtherapeutic levels were identified in 19 samples from 12 patients. Among eight patients receiving prophylactic posaconazole with trough levels below 0.7 mg/L, two experienced breakthrough invasive fungal infections. Diarrhea, sampling before steady state, medication non-adherence, and poor oral intake were significantly more frequent in cases with subtherapeutic posaconazole levels (p = 0.022). Among six measurements with posaconazole concentrations exceeding 3.75 mg/L, an adverse effect attributable to posaconazole was observed in only one of the five patients with these elevated levels. CONCLUSION: The findings of this real-world assessment suggest that posaconazole TDM may play a critical role in optimizing both prophylaxis and treatment, particularly among patients at risk for subtherapeutic exposure.