Relationship between blood posaconazole concentration and serum potassium levels

Some studies have suggested a correlation between posaconazole (PSCZ) concentration and efficacy in preventing fungal infections; the international guidelines recommend therapeutic drug monitoring. However, few studies have investigated the association between PSCZ concentration and its representative adverse effect of hypokalemia. This study aimed to measure serum PSCZ concentrations and investigate the relationship between this parameter and hypokalemia.

This study was conducted at Aichi Medical University Hospital. All patients in the hematology department who orally received PSCZ were included, wherein their trough serum concentrations (Cmins) of PSCZ were measured using high-performance liquid chromatography. Serum potassium levels were monitored for 60 days following PSCZ initiation. Hypokalemia was defined as serum potassium levels of <3.0 mEq/L and ≥10.0 % decreases from baseline following PSCZ administration.

A total of 24 patients were included. The incidence of hypokalemia was 41.7 %. The median PSCZ concentrations were comparable between patients who developed hypokalemia and those who did not (2.5 μg/mL vs 2.4 μg/mL, p = 0.98). In both groups, approximately 80 % of the patients (80.0 % vs. 78.6 %, p = 0.98) showed PSCZ concentrations below 4.0 μg/mL. No significant correlations were found between PSCZ Cmin and the rate of serum potassium level reduction (γ = -0.21, p = 0.32) or minimum potassium level (γ = -0.03, p = 0.88).

PSCZ might cause hypokalemia regardless of Cmin; clinicians in hematology should remain vigilant.