Characterization of Polymorphic and Blended Drugs by Physical-Analytical Properties

The polymorphs of Tolbutamide and Nifedipine were differentiated by measuring their unique physical properties. Differential Scanning Calorimetry (DSC) and Dielectric Analysis (DEA) verified the variations in these compounds with different crystal structures but the same chemical constituents. The crystalline-amorphous content of the polymorphs were determined based on a new DEA protocol. Solubility (w/w ) and spectroscopic methods clearly distinguished these drugs and compared favorably with the photomicrography of the polymorphs. Powder X-ray Diffraction (PXRD) analysis succintly showed differences in the various types of polymorphs. Scanning Electron Microscopy (SEM) supported the structural distinction and solubility. The FTIR spectra of all the polymorphs were reproducible and illustrated differences between tolbutamide and nifedipine but not within its polymorphs. The analytical techniques developed in this study were also used in analyzing blends of drugs and excipients, e.g. Aspirin and Polyethylene Glycol (PEG). Co-crystallization of drugs with PEG, an excepient, was measured with increases in the PEG heat of fusion beyond its blended concentration. The extra heat associated with the PEG heat of fusion is due to the crystallization of the amorphous drugs in the PEG matrix. These unique co-crystallized blends will yield enhanced drug delivery since PEG is very water solubl