Surface Modification Improves Tablet Tensile Strength

Achievement date: 

By examining tensile strength values, researchers at the Center for Structured Organic Particulate Systems (C-SOPS), a National Science Foundation (NSF) Engineering Research Center (ERC) based at Rutgers University in partnership with New Jersey Institute of Technology, Purdue University, and the University of Puerto Rico-Mayaguez, have discovered that dry coating an active pharmaceutical ingredient (API) increases the tablet strength regardless of excipient particle size. A two-property phase map correlated powder flowability with tablet strength to explore flow function coefficient (FFC) values of different blends consisting of fine excipients as well as coarse excipients. By coating APIs, the highest tensile strength values were observed.


Direct compression has been widely used to make pharmaceutical tablets; however, this method cannot be employed for most fine APIs due to their poor flow. With surface modification via dry coating, a more efficient approach to improving powder flowability is established. Dry coating acetyl-para-aminophenol (APAP)—better known as acetaminophen—improves packing and flow properties regardless of excipient particle size. The use of fine excipients also aids in improving tablet compactibility, assuring that high API loading blends are suitable for direct compaction. This has significant potential for cost savings by eliminating extra granulation steps that would otherwise be required.


FFC-Tensile Strength phase maps of placebo blends; blends without silica; blends with coated extra strength acetaminophen (mAPAP); and blends coated with all three principal components were studied for 60% API loading containing fine as well as coarse excipients. Blends without silica have very low FFC values (2.8 and 3.8); and because they are cohesive, they will not flow well during tableting processes. After adding silica, these blends show increased FFC values (4.5 and 5.2). After API coating, the FFC values increase substantially to 9.1 and 9.5, respectively, which is much higher than the reference values corresponding to Avicel 102.