RELEASE PROBLEMS FOR NIFEDIPINE IN THE PRESENCE OF SOLUPLUS

Nifedipine/soluplus co-precipitates were prepared at 1:9 and 1:1 weight ratios, using the solvent method, with the aim to obtain an improvement of the drug release. The release, though accelerated with respect to physical mixtures and pure drug, resulted slow with respect to similar systems containing soluplus and are characterized by the appearance in suspension of micro-particulates that, at the optical microscope, revealed a large variety of shapes typical of flower-like aggregates, not previously reported. For comparison systems were also prepared with PVP K30 and sucrester P1670 and two mixtures, without any evidence of this last phenomenon. The systems were studied by thermal (differential scanning calorimetry ? DSC, thermomicroscopy ? HSM) and spectroscopic (SEM, FT-IR, micro-Raman) analysis. Slow release of nifedipine and formation of colloidal micro- particulates were hypothesized due to the gelling tendency of soluplus associated to drug/polymer multi-site-interactions: when one of these parameters is absent in the system the two phenomena could not be observed together, such as in the case of PVP K30 or sucrester P1670, when used as carriers for nifedipine release.