Investigation of Enhancement of Solubility of Norfloxacin β-Cyclodextrin in Presence of Acidic Solubilizing Additives

The present study is aimed at improving the solubility of a poorly water-soluble drug, norfloxacin by incorporating solubilizing additives such as ascorbic acid and citric acid into the β-cyclodextrin complexes. Norfloxacin, being amphoteric in nature, exhibits a higher solubility at pH below 4 and above 8. Addition of substances like ascorbic acid and citric acid in β-cyclodextrin complexes reduces the pH of the immediate microenvironment of the drug below pH 4. In the present work, β-cyclodextrin complexes of norfloxacin were prepared along with solubilizing additives such as citric acid and ascorbic acid in various proportion and the dissolution profile was performed in both HCl buffer, pH 1.2 and phosphate buffer, pH 7.4. The results have shown an enhanced dissolution rate in both media. DSC and IR spectral studies performed on the solid complexes have shown that there is no interaction of the drug with the additives and β-cyclodextrin. Disc diffusion studies have shown larger diameters of zone of inhibition indicating a greater diffusivity of the drug into the agar medium. Keywords: Norfloxacin, dissolution rate, β-cyclodextrin, solubility, citric acid, ascorbic acid