Supercritical fluid technology as a strategy for nifedipine solid dispersions formulation: In vitro and in vivo evaluation.

Supercritical fluid technology (SFT) is an insufficiently investigated approach for the production of solid dispersions, it is environmentally acceptable and has a high potential for application in the pharmaceutical industry. The aim of this work was to formulate and characterize nifedipine solid dispersions (SDs) produced by the SFT and compare the results with ones obtained by the classical solvent based kneading method. The following in vitro tests were conducted: assay and yield, solvent residues, solid state characterization (FTIR, DSC, XRD), flowability, hygroscopicity, solubility, dissolution and stability. Additionally, bioavailability was examined on an animal model (Wistar rats). The formulation selection for in vivo study was performed using the multilevel categoric experimental design and the health risk assessment. Solid state characterization revealed that formulation obtained by the SFT method and higher ratio of polymer (1:5) have had nifedipine in completely amorphous form. Polymer ratio and method of SDs preparation do influence the investigation characteristics. Dissolution rate was fastest in SDs prepared by the SFT and higher polymer ration (1:5). In vivo data of selected SDs prepared by the kneading (ratio 1:1) and the SFT (ratio 1:5) showed alteration in pharmacokinetic profile after i.v. and p.o. application.