Treatment by Posaconazole Tablets, Compared to Posaconazole Suspension, Does Not Reduce Variability of Posaconazole Trough Concentrations.

The delayed-release tablet formulation of posaconazole (POS-tab) results in higher plasma POS trough concentrations (C) than the oral suspension (POS-susp), which raises the question of the utility of therapeutic drug monitoring (TDM). We aimed to compare the variability of the POS C for the two formulations and identify determinants of the POS-tab C and its variability. Demographic, biological, and clinical data from 77 allogeneic hematopoietic stem cell transplant patients (874 C) treated with POS-tab ( = 41), POS-susp ( = 29), or both ( = 7) from January 2015 to December 2016 were collected retrospectively. Interpatient and within-subject coefficients of variation (CVs) of the C adjusted to dose (D) were calculated for each formulation. Between-group comparisons were performed using a linear mixed effects model. The POS C was higher for the tablet than for the suspension (median [25th-75th percentile]: 1.8 [1.2-2.4] mg/liter versus 1.2 [0.7-1.6] mg/liter,  < 0.0001). Interpatient CVs for the tablet and suspension were 60.8 versus 63.5% ( = 0.7), whereas within-subject CVs were 39.7 and 44.9%, respectively ( = 0.3). Univariate analysis showed that age and treatment by POS-tab were significantly and positively associated with the POS C, whereas diarrhea was associated with a diminished POS C Multivariate analysis identified treatment with POS-tab and diarrhea as independent factors of the POS C, with a trend toward a lower impact of diarrhea during treatment with POS-tab ( = 0.07). Despite increased POS exposure with the tablet formulation, the variability of the POS C was not significantly lower than that of the suspension. This suggests that TDM may still be useful to optimize tablet POS therapy.