Soluble Complex Formation of 6-Ethyl-2, 3, 6, 9-tetrahydro-3-methyl-2, 9-dioxothiazolo-[5, 4-f] quinoline-8-carboxylic Acid (Tioxacin) with Aliphatic Amines

Abstract

Interactions of antibacterial 6-ethyl-2, 3, 6, 9-tetrahydro-3-methyl-2, 9-dioxothiazolo-[5, 4-f] quinoline-8-carboxylic acid (tioxacin) with aliphatic amines such as ethylenediamine, n-propylamine, ethanolamine, piperazine, piperidine, and morphorine were studied in water and in solid state. Soluble complex formations between tioxacin and the amines were ascertained by the solubility method, powder X-ray diffractometry, thermal analyses, and IR spectroscopy. Increase in aqueous solubility of tioxacin was found to be proportional to the basicity of the amine, which was reflected in the magnitude of the complex stability constant. The dissolution rate of the complex was significantly higher than that of thioxacin itself in water. Absorption studies in dogs suggested that the amine complex may have a great utility as a rapid dissolving form of tioxacin in oral administration.