Insights into drug precipitation kinetics during in vitro digestion of a lipid-based drug delivery system using in-line raman spectroscopy and mathematical modeling.

PURPOSE

To determine drug precipitation during in vitro lipolysis of a lipid-based drug delivery system (LBDDS) using Raman spectroscopy as a real-time monitoring technique. A second aim was to describe the kinetics of lipolysis-triggered drug precipitation using a theoretical nucleation and growth model.

METHODS

A model LBDDS containing different concentration of fenofibrate was digested in vitro and drug precipitation was determined after ultracentrifugation and nanofiltration (off-line methods), as well as by Raman spectroscopy (in-line method). Subsequently, a theoretical nucleation and growth model was fitted to the obtained drug crystallization profiles by considering the lipolysis-triggered change in drug solubility.

RESULTS

Compared with standard off-line measurements, Raman spectroscopy enabled a more robust and highly time-resolved analysis of lipolysis-triggered drug precipitation. Although the formulation was rapidly digested, fenofibrate remained in a supersaturated state for several minutes before beginning to crystallize. The in vitro digestion results were in excellent agreement with the theoretical model (R (2)  > 0.976).

CONCLUSIONS

The combination of real-time Raman spectroscopy and mathematical modeling provided insights into the kinetics of lipolysis-triggered drug crystallization. This knowledge allows a better biopharmaceutical understanding and will, ultimately, lead to the improved development of lipid-based drug formulations.