Identification of a pharmacokinetic interaction between teicoplanin and sulfo-butyl ether-beta-cyclodextrin, an excipient in the intravenous posaconazole formulation

Patients undergoing hematopoietic stem cell transplantation (HSCT) often receive multiple antibiotics and antifungals concurrently, making it crucial to understand their potential pharmacokinetic interactions of these agents. We report here an interaction between the glycopeptide antibiotic teicoplanin (TEIC) and sulfo-butyl ether-{beta}-cyclodextrin (SBECD), a solubilizing excipient in the intravenous formulation of posaconazole (PSCZ). We performed a single-center retrospective analysis of patients who underwent HSCT and received oral and intravenous PSCZ during TEIC therapy. The associations between PSCZ administration and TEIC concentration-to-dose (C/D) ratios were evaluated using linear mixed-effects models. We also examined the effects of intravenous PSCZ and SBECD on TEIC pharmacokinetics in rats by assessing the area under the concentration-time curve (AUC) and urinary excretion of total TEIC and its components. In addition, molecular docking and in vitro protein-binding assays were conducted to investigate the interaction between TEIC and SBECD. In patients who underwent HSCT, TEIC C/D ratio was significantly lower following intravenous PSCZ administration than without administration. In contrast, the effect of oral PSCZ administration relative to non-administration was not statistically significant. In rats, intravenous PSCZ and SBECD decreased the AUC of TEIC and increased urinary excretion, particularly in the A2 group. Docking simulations indicated that the hydrophobic side chain of TEIC A2-2 fit within the SBECD cavity, and in vitro assays confirmed SBECD concentration-dependent increases in TEIC unbound fractions. The co-administration of intravenous PSCZ containing SBECD may reduce TEIC protein binding, thereby enhancing renal excretion.