The influence of HPMC viscosity as FRC parameter on the release of low soluble drug from hydrophylic matrix tablets.

The importance of functionality-related characteristics (FRC) of hydroxypropyl methylcellulose (HPMC) described in the pharmacopeia monograph can be evaluated only for selected formulation or technological process. The aim of our work was to investigate the influence of apparent viscosity as one of the FRC for two batches of the same HPMC grade on the release properties of diclofenac sodium from HPMC matrix tablets. Our results show that two batches of HPMC differ in viscosity significantly and as a consequence, the significant differences were observed in the release profiles as well. HPMC-B sample has higher viscosity and therefore higher average molecular weight, thus the erosion and drug release were slower compared to HPMC-A sample with lower apparent viscosity. It can be concluded that batch-to-batch viscosity variation of the same HPMC grade can lead to the different release profiles; therefore the specification limits of some FRC should be postulated during the development of each individual formulation. However, the viscosity interval as FRC can not be generalized, because it is different for different tablet compositions.