Effect of insoluble excipients on performance of direct compression controlled release matrices

This work aimed the assessment of the effect of the insoluble diluents microcrystalline cellulose (MCC) and dicalcium phosphate dihydrate (DCP) on performance of hydrophilic controlled release matrices of hydroxypropyl methylcellulose (HPMC) and Noveon AA1. The performance of powder blends and matrix tablets was determined using dissolution and compactibility profiles and the powders compressibility index. Increasing proportions of DCP produce initially a decrease and thereafter an increase in the dissolution rate of metronidazole. Noveon AA1 matrices displays n values near to zero order release (n = 0.95), decreasing gradually up to 0.68 with increasing proportions of DCP. Metronidazole/MCC matrices containing Noveon AA1 display an almost 100% greater compactibility than those containing HPMC. MCC potentiates the agglutinant functionality of both matrix-forming polymers. Addition of a brittle material such as DCP displays a modest effect on metronidazole matrices compactibility. MCC reduces the effect of Noveon AA1 to decrease the flowability of metronidazole/HPMC powder blends. The effect of DCP is a dramatically increase in flowability of blends of metronidazole containing high proportions of Noveon AA1 (25%).