Cooperative effect of polyvinylpyrrolidone and HPMC E5 on dissolution and bioavailability of nimodipine solid dispersions and tablets.

Solid dispersion (SD) systems have been extensively used to increase the dissolution and bioavailability of poorly water-soluble drugs. To circumvent the limitations of polyvinylpyrrolidone (PVP) dispersions, HPMC E5 was applied in the formulation process and scaling-up techniques, simultaneously. In this study, SD of nimodipine (NMP) and corresponding tablets were prepared through solvent method and fluid bed granulating one step technique, respectively. Discriminatory dissolution media were used to obtain reliable dissolution results. Meanwhile, the stability study of SDs was investigated with storage under high temperature and humidity conditions. Moreover, the solubility of SDs was measured to explore the effect of carriers. The preparations were characterized by DSC, PXRD, and FTIR. Dramatical improvements in the dissolution rate of NMP were achieved by the ingenious combination of the two polymers. Binary NMP/PVP/HPMC-SDs released steadily, while the dissolution of single NMP/PVP-SDs decreased rapidly in water. The fluid-bed tablets (FB-T) possessed a similar dissolution behavior to the commercial Nimotop™ tablets. The characterization patterns implied that NMP existed in an amorphous state in our SDs. Furthermore, the results of stability tests suggested a better stability of the binary SDs. A special cooperative effect of PVP and HPMC was discovered on dissolution characteristics of NMP SDs and tablets, which could be extended to other drugs henceforth. Finally, the bioavailability of FB-T was evaluated in beagle dogs with Nimotop™ as the reference, and the results showed a higher value for FB-T.