Abstract—The interaction of antibiotic oxytetracycline hydrochloride (OTC) with calcium chloride has been investigated by conductometric, spectrophotometric and in vivo, methods under equilibrium conditions. The interaction of OTC with calcium ion in water and in methanol solvents has been found to form two complexes 1:1 and 2:1 (metal to ligand molar ratio) conductometricallyand the values of Kf has been calculated from conductivity measurements at 293.15, 298.15, 303.15 and 308.15 K, Gibbs free energy of formation, enthalpy and entropy change of complexation were determined from the temperature dependence of the formation constant. Also Kf calculated from the absorption spectra of CaCl₂ – OTC complexes in methanol solvent at 293.15 K indicates the formation of 2:1. In case of in-vivo studies there is no significant change was observed in the mean value of serum ionized calcium of the treated rats, this indicates that the values obtained from Conductometric and spectrophotometric studies are accepted because the stability constant values were found to be in biologically active range. All values are discussed.

Cite: Elsayed T. Helmy, Esam A. Gomaa, Elsayed M. Abou Elleef, and Amr Negm, " Conductometric, Spectrophotometric and In vivo Investigation of the Interaction of Ca(II) Ion with Oxytetracycline Hydrochloride" International Journal of Pharma Medicine and Biological Sciences, Vol. 4, No. 3, pp. 197-203, July 2015. doi: 10.18178/ijpmbs.4.3.197-203