Preparation and Characterization of Spironolactone-Avicel PH 101 physical mixtures and adsorbates.

The objective of this study was to investigate the effect of the surface adsorption of poorly soluble drug spironolactone onto an inert matrice Avicel PH 101 as a technique for improving the drug dissolution. The loaded mixtures of spironolactone with Avicel PH 101 were prepared by solvent deposition method. Adsorbate systems containing (1:1, 1:2 and 1:3) w/w drug/adsorbent ratios were prepared. adsorbates were scrapped and powdered. Also physical mixtures of different w/w drug/carrier ratios (1:1, 1:2 and 1:3) were prepared by simple mixing. The physicochemical characterization of the systems using differential scanning calorimetry (DSC) and powder X-ray diffraction was carried out to detect possible interaction between the drug and the carrier, moreover, quantitative solubility and in- vitro dissolution studies of spironolactone alone and in physical mixtures or adsorbates were studied in simulated gastric fluid (SGF) of PH 1.2 and in simulated intestinal fluid (SIF) of PH 7.4.
The reduction of drug peaks in DSC profile of the adsorbate particles suggests the transformation of crystalline spironolactone into an amorphous from. The same result is indicated by X-ray diffraction, where the adsorbate mixture showed smaller characteristic peaks than those of the plain drug with reduced intensity indicating incomplete transformation of the drug to the amorphous state. The study showed a little improvement in the dissolution pattern of the drug in case of the adsorbate and a more improvement in case of physical mixtures.