Probing in Vitro Release Kinetics of Long-Acting Injectable Nanosuspensions via Flow-NMR Spectroscopy

Novel treatment routes are emerging for an array of diseases and afflictions. Complex dosage forms, based on active pharmaceutical ingredients (APIs) with previously undesirable physicochemical characteristics, are becoming mainstream and actively pursued in various pipeline initiatives. To fundamentally understand how constituents in these dosage forms interact on a molecular level, analytical methods need to be developed that encompass selectivity and sensitivity requirements previously reserved for a myriad of in vitro techniques. The knowledge of precise chemical interactions between drugs and excipients in a dosage form can streamline formulation development and process screening capabilities through the identification of properties that influence rates and mechanisms of drug release in a cost-effective manner, relative to long-term in vivo studies. Through this work, a noncompendial in vitro release (IVR) method was developed that distinguished the presence of individual components in a complex crystalline nanosuspension environment. Doravirine was formulated as a series of long-acting injectable nanosuspensions with assorted excipients, using low- and high-energy wet media milling methods. IVR behavior of all formulation components were monitored using a robust continuous flow-through (CFT) dissolution setup (USP-4 apparatus) with on-line ¹H NMR end-analysis (flow-NMR). Results from this investigation led to a better understanding of formulation parameter influences on nanosuspension stability, surface chemistry, and dissolution behavior. Flow-NMR can be applied to a broad range of dosage forms in which specific molecular interactions from the solution microenvironment require further insight to enhance product development capabilities.