An Imaging Toolkit for Physical Characterization of Long-Acting Pharmaceutical Implants

In pharmaceutical development alternative drug delivery modalities are being increasingly employed. One example is an implant, which achieves gradual drug release in patients over a period of many months or years. Due to the complexity of these long-acting formulations, advanced physical characterization methods are desirable as screening tools during protracted formulation development. Imaging methods are of particular interest due to their ability to interrogate the structure and composition of implants spatially across multiple length scales (macro, micro, nano). In this work, spatiochemical imaging is shown to interrogate many crucial drug product attributes of solid implants: overall implant structure, drug distribution, micro-domain size and orientation, agglomeration, porosity and defects, drug/excipient interface, dissolution process, and release mechanism. Imaging methods facilitate a detailed understanding of the process/structure correlation to inform on formulation selection, process parameter optimization, and batch consistency. Numerous case studies of implant applications with imaging are discussed. Methods utilized are X-ray computed tomography (XRCT), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) imaging, and Raman microscopy. The imaging data is complemented with solid-state nuclear magnetic resonance (ssNMR). Altogether, these examples demonstrate that complementary imaging methods are highly effective for analyzing complex and novel pharmaceutical modalities such as solid implants.