Colon targeted drug delivery systems have gained a great deal of attention as potential carriers for the local treatment of colonic diseases with reduced systemic side effects and also for the enhanced oral delivery of various therapeutics vulnerable to acidic and enzymatic degradation in the upper gastrointestinal tract. In recent years, the global pharmaceutical market for biologics has grown, and increasing demand for a more patient-friendly drug administration system highlights the importance of colonic drug delivery as a noninvasive delivery approach for macromolecules. Colon-targeted drug delivery systems for macromolecules can provide therapeutic benefits including better patient compliance (because they are pain-free and can be self-administered) and lower costs. Therefore, to achieve more efficient colonic drug delivery for local or systemic drug effects, various strategies have been explored including pH-dependent systems, enzyme-triggered systems, receptor-mediated systems, and magnetically-driven systems. In this review, recent advancements in various approaches for designing colon targeted drug delivery systems and their pharmaceutical applications are covered with a particular emphasis on formulation technologies.

Three-dimensional printing (3DP) technology allows the fabrication of 3D objects with various geometrics in a layer-bylayer process. Some advantages of 3DP methods over the conventional manufacturing processes include the customization of medicines with individually adjusted doses, the ability to fabricate the sophisticated and complex solid dosage forms, on-demand manufacturing, and cost-effectiveness. Furthermore, recent years have seen an increasing interest in applying 3DP technology to the pharmaceutical manufacturing of drug products and development of various drug delivery systems. However, although 3DP technology exhibits many potential medical and economic benefits, there are also some technical and regulatory challenges restricting the wide applications of 3DP technology to pharmaceutical products. Accordingly, continuous innovation and refinement in 3DP methods are needed to overcome the current limitations and facilitate patientspecific health care with on-demand tailored medications in the future. This review introduces some 3DP techniques suitable for pharmaceutical manufacturing and also their applications to the development of drug dosage forms, indicating the feasibility of this technology in regular commercial production.