Solid dosage formulations remain the most important dosage forms for pharmaceuticals. In all solid formulations, the most important properties are the stability and bioavailability of the active pharmaceutical ingredient (API). Different polymorphs of API crystals often differ in the physicochemical properties like chemical and physical stability, solubility and dissolution. These differences leads to variability in drug efficacy, bioavailability, and even toxicity. A thorough understanding of how excipients and physical processing impact the polymorphism, stability, and dissolution rate of API is crucial to accelerate drug development and regulatory approval. However, currently no technology can monitor the dynamic chemical changes of solid formulation in situ at sub micrometer resolution during processing or dissolution.
SRS microscopy is a powerful chemical imaging technique that can potentially address these challenges. In particular, it allows label-free imaging of APIs and excipients at high spatial and temporal resolution. Here we present our recent work on using hyperspectral SRS microscopy to resolve polymorphic changes of APIs at low drug loading. In addition, we demonstrate that we can monitor the dissolution of individual entecavir drug crystals in a slow-release implant drug sample. Together, these experiments demonstrate that hyperspectral SRS microscopy can be a valuable technique for resolving details of drug instability and drug dissolution in formulation research.
|