Preparation and evaluation of nifedipine solid dispersions

Oral drug delivery is the simplest and easiest way of administering drugs. However, if the drug being administered has limited aqueous solubility it can result in poor bioavailability. Solid dispersion method was originally used to improve the dissolution properties and the bioavailability of poorly water- soluble drugs by dispersing them into water-soluble carriers. This study aims to enhance the solubility of nifedipine, a poorly water-soluble drug, by solid dispersion technique using poloxamer 188 as a carrier. The solid dispersions were prepared by fusion method using various drug to polymer ratios. Moreover, the influence of drug-to-polymer ratio on drug solubility was studied. The resultant formulations were characterized by Fourier-transformed infrared spectroscopy (FT-IR), Powder X-ray diffractometry (PXRD) as well as solubility study. FTIR results indicated a lack of significant interaction between the drug and the carrier in the solid dispersions. Compared with pure drug and physical mixtures, the solubility of nifedipine in solid dispersions was enhanced dramatically which indicates that the solubility enhancement is not due to the solubilizing effect of the carrier alone but it may be attributed to the reduction of the crystallinization of nifedipine in the hydrophilic matrix which could be confirmed by PXRD results.