The aqueous solubility of ofloxacin in the presence of metallic cations

Ofloxacin belongs to the class of fluoroquinolones which has found widespread use in the treatment of microbial infections resistant to  other antibiotics. However, metallic cations and anti-acids have been found to adversely affect the bioavailability and antibacterial activity of ofloxacin. Many reasons have been suggested to explain the observed effects. In order to gain further understanding of how ofloxacin-metallic cation interaction affects ofloxacin availability and activity, the aqueous solubility of ofloxacin was investigated in the presence of some metallic cations spectrophometrically in this study. All the cations investigated increased the aqueous solubility of ofloxacin to varying extents. Ferrous sulphate produced the greatest increase in the solubility of ofloxacin. It was followed by ferric ammonium citrate, magnesium sulphate, aluminium hydroxide and calcium carbonate. Potassium chloride and sodium bicarbonate produced very slight increases. In all the cases, the solubility of ofloxacin increased as the amount of each metallic cation increased. The observed results can be attributed to formation of soluble ionic ofloxacin carboxylate salts and complexes of the metallic cations. The implication of such increase of the aqueous solubility of ofloxacin in the presence of metallic cations on the bioavailability and antibacterial activity of ofloxacin is discussed.