Preformulation and evaluation of multi-layer tablets

The tablet is the most common drug formulation in the pharmaceutical industry. With the invention of new pharmaceutical tablet compression technologies, more advanced tablet designs, such as multi-layer tablets (MLTs), have been reported.

This review focuses on (1) the advantages and manufacturing challenges of MLTs, (2) the underlying mechanisms in compaction, and (3) technologies for the evaluation of adhesion between layers, which is the most important factor in quality of MLTs.

The use of MLTs is gradually increasing due to the variety of drug combinations in use and the complexity of the release design of the different formulations. Essentially, an MLT is a combination of monolithic tablets, all of which must have good mechanical properties. Unlike monolithic tablets, the interfacial adhesion of MLTs significantly impacts their quality. Therefore, the excipients and their mixtures in an MLT must be evaluated for a variety of physical properties. Additionally, evaluation methods that measure interfacial adhesion can ensure the quality of MLTs.