Screening of several excipients for direct compression of tablets: A new perspective based on functional properties
Excipients are widely used to formulate solid drug forms by direct compression. However, the powderforming and tableting properties of these excipients are affected by the presence of lubricants and active ingredients. In this study, a screening methodology was employed to test the performance of an excipient for direct compression. The effects of three lubricants (magnesium stearate, stearic acid and talc) on the compressibility and compaction of these excipients were assessed by the compressibility index and lubricant sensitivity ratio, respectively. Likewise, the dilution potential in blends with a poorly compactible drug such as acetaminophen was also assessed. Finally, the elastic recovery of tablets was evaluated five days after production. All lubricants increased the compressibility of these excipients and improved their flowability. However, hydrophobic lubricants such as magnesium stearate had a marked negative effect on compactibility, especially in plastic-deforming and more regularlyshaped materials with a smooth surface such as Starch 1500. Alginic acid, rice and cassava starches had the largest elastic recovery (>5%), indicating a tendency to cap. Moreover, highly plastic deforming materials such as sorbitol and polyvinylpyrrolidone (PVP-K30) exhibited the best dilution potential (~10%), whereas alginic acid showed a very high value (~70%). In terms of performance, sorbitol, PVP-K30, Avicel PH-101, sodium alginate and pregelatinized starch were the most appropriate excipients for the direct compression of drugs.