Formulation approaches for colon-specific drug delivery: conventional to nanocarrier systems

The development of colon-targeted drug delivery systems (CDDS) has gained increasing attention due to their potential to improve therapeutic outcomes for diseases such as inflammatory bowel disease (IBD), irritable bowel syndrome (IBS), colorectal cancer, and other colonic disorders. Targeted delivery to the colon offers the advantages of site-specific action, reduced systemic side effects, and improved patient compliance. However, several physiological barriers, such as variable pH, microbial metabolism, enzymatic degradation, and transit time, pose significant formulation challenges. This review provides a comprehensive overview of conventional and advanced formulation strategies for colon-targeted drug delivery. Various approaches, including pH-responsive systems, time-dependent delivery, microbially triggered systems, prodrug strategies, pressure-controlled devices, and nanotechnology-based delivery platforms, are critically discussed. Additionally, the emerging role of natural polysaccharide-based systems and innovative hybrid formulations is highlighted. Comparative analysis of different strategies is presented to guide future formulation design. Advancements in nanotechnology and biomaterials offer promising opportunities to overcome existing challenges and enable precise and efficient colon-targeted drug delivery. Further research is warranted to translate these innovative systems into clinically viable therapies with improved efficacy and patient outcomes.