Chitosan, a biopolymer derived from the partial deacetylation of chitin, has attracted significant interest as a sustainable pharmaceutical excipient due to its biodegradability, biocompatibility, and diverse functional attributes. Recent breakthroughs have explored the valorization of chitosan biowaste in pharmaceutical formulations, particularly in oral drug delivery, leveraging its tunable physicochemical properties. This review thoroughly examines recent advancements and patented innovations in chitosan-based drug delivery by conducting an extensive literature search using PubMed, Scopus, Google Scholar, and ClinicalTrials.gov, and analyzing patents from Espacenet and USPTO databases. Key findings reveal that chitosan’s molecular weight, degree of deacetylation, and source critically influence its pharmaceutical applications, including drug encapsulation, mucoadhesion, and controlled release. Novel formulations, such as chitosan-silicate coprecipitates, polyelectrolyte complexes, and nanostructured chitosan carriers, have enhanced drug solubility, bioavailability, and stability. However, challenges persist in optimizing extraction methods, ensuring batch-to-batch reproducibility, and expanding its pharmaceutical applications beyond conventional uses. Future research should focus on eco-friendly extraction techniques, novel chemical modifications to enhance functionality, and clinical evaluation of chitosan-based drug formulations to maximize its potential as a sustainable pharmaceutical excipient.

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