Correlation between the viscoelastic properties of the gel layer of swollen HPMC matrix tablets and their in vitro drug release

Abstract

Drug release from hydroxypropyl methylcellulose (HPMC) hydrophilic matrix tablets is controlled by drug diffusion through the gel layer of the matrix-forming polymer upon hydration, matrix erosion or combination of diffusion and erosion mechanisms. In this study, the relationship between viscoelastic properties of the gel layer of swollen intact matrix tablets and drug release was investigated. Two sets of quetiapine fumarate (QF) matrix tablets were prepared using the high viscosity grade HPMC K4M at low (70 mg/tablet) and high (170 mg/tablet) polymer concentrations. Viscoelastic studies using a controlled stress rheometer were performed on swollen matrices following hydration in the dissolution medium for predetermined time intervals. The gel layer of swollen tablets exhibited predominantly elastic behavior. Results from the in vitro release study showed that drug release was strongly influenced by the viscoelastic properties of the gel layer of K4M tablets, which was further corroborated by results from water uptake studies conducted on intact tablets. The results provide evidence that the viscoelastic properties of the gel layer can be exploited to guide the selection of an appropriate matrix-forming polymer, to better understand the rate of drug release from matrix tablets in vitro and to develop hydrophilic controlled-release formulations.

Keywords:

• Controlled stress rheometer
• matrix tablets
• viscoelasticity
• swollen tablets
• gel layer
• in vitro release

Acknowledgements

The authors would like to thank the Faculty of Pharmacy at the University of Jordan for using the plate–plate geometry as an accessory for our CSR. The authors are also thankful to Dr. Tao Yu from the School of Pharmacy at Queen’s University Belfast for his valuable input on rheological studies.

Disclosure statement

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.