Advanced Tablet Coating Technique: Dip Coating Technique

The dip coating technique is a widely used method in thin film deposition, particularly in industries like electronics, optics, and materials science. This process involves immersing a substrate material into a liquid solution or suspension (the coating material) and then slowly withdrawing it at a controlled speed. As the substrate is pulled out, a thin film of the coating material adheres to its surface due to capillary action, forming a uniform layer upon subsequent drying or curing. Factors like viscosity, surface tension, and concentration of the coating solution, as well as withdrawal rate and drying techniques, are carefully controlled to achieve the desired film characteristics. This technique offers advantages such as simplicity, cost- effectiveness, and scalability for large-scale production. However, challenges related to controlling film thickness, achieving uniformity, and handling high-viscosity coatings exist and require precise process optimization(1). In this process, the cores are held in a suitable device (e.g. baskets) and dipped into the coating solution and then dried carefully to avoid sticking to each other. For better or heavier coats, the dipping and drying process may need to be repeated multiple times one after the other. There are several dipping arrangements available, some of which include small suction tubes that hold the tablets apart until the drying process is complete, after which you can add more tablets or start the recoating cycle(2). The coating techniques used in tablet production greatly influence the aesthetic qualities such as colour, texture, mouthfeel, and taste masking. However, these techniques have certain limitations and drawbacks. To overcome these limitations, Tablet in Tablet is considered one of the best alternatives. The objective of this study is to comprehensively review the formulation, characterization, and challenges associated with the development of Tablet in Tablet dosage form. Currently, there are only a few patents filed or granted on this topic, including the Tablet in Tablet of cyclophosphamide and capecitabine. Our focus is to provide the rationale behind the development of such dosage forms (3).