Preparation and evaluation of a sustained-release formulation of nifedipine HPMC tablets

A nifedipine (NF) polyethylene glycol (PEG) solid dispersion was prepared. Using this solid dispersion, NF hydroxypropylmethylcellulose (HPMC) matrix tablets were prepared. Both the high-viscosity grade HPMC (Methocel K15M) and low-viscosity grade HPMC (Methocel K100) were applied in the tablets to form the matrix. The dissolution and absorption of NF from the tablet were evaluated as a formulation that had a sustained release over 24 hr. The Hixson-Crowell equation and Higuchi equation were used to investigate the dissolution mechanism, and the erosion and diffusion codependent mechanism was established. Adalat GITS 30 was used as a reference dosage form. Each beagle dog was also administered an intravenous injection to obtain the pharmacokinetics parameters. The Loo-Riegelman method was applied to study the in vitro/in vivo correlation of the tested tablets and Adalat GITS 30, and significant correlation was proved. Absolute bioavailability and comparative bioavailability of the tested tablet were studied. The results indicated that the NF HPMC tablet could be an ideal 24-hr sustained-release formulation.