Nifedipine di-matrix depot tablets prepared by compression coating for obtaining zero-order release

Compression coating is a possible process for obtaining zero-order release. Nifedipine compression-coated (CC) di-matrix depot tablets were prepared from a single punch tablet press with low viscosity hydroxypropyl cellulose (HPC-L) as the inner polymer, and with middle viscosity hydroxypropyl cellulose (HPC-M), HPC-L and Eudragit RSPO as outer polymers. The release behavior and mechanisms in vitro of the final tablets were investigated, and gravimetric analysis was used to study the release mechanism. The fast release of the core depot and slow release of the outer depot with time formed total zero-order release. The results showed that the formulation presented ideal zero-order release at the weight ratio of nifedipine 3:5 (core: layer), the combination of HPC-L and HPC-M (56:25) in the outer depot, and with the core depot placed in the center. The CC tablets released to more than 95% in 24?h and fitted a zero-order model with the equation M_t/M^∞?=?0.038t (R²?=?0.98555). In conclusion, zero-order release of nifedipine over 24?h could be achieved by applying polymer HPC-L and HPC-M with the compression coating technique.