Physicochemical Properties and Stability in the Acidic Solution of a New Macrolide Antibiotic, Clarithromycin, in Comparison with Erthyomycin

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Clarithromycin (6-O-methylerthromycin), a new 14-membered macrolide antibiotic, has been studied to clarify its physicochemical properties and stability in acidic solution, as compared with erythromycin (EM).The solubility of clarifhromycin (CMC) in distilled water was lower than that of EM and decreased with increasing temperature. The solubilities of CAM and EM in the phosphate buffer solution at 37℃ decreased with an increasing pH and kept constant above pH 9. From pH-solubility profiles, the dissociation constants of CAM and EM were determined to be 8.76 and 8.36,respectively. The partition coefficient of CAM took a higher value than that of EM and increased with an increasing pH.In the acidic splution, the decomposition of CAM and EM obeyed the pseudo-first order kinetics. From the decomposition rate constants, the half life (T_<1/2>) of CAM and EM were determined. In pH 1.39,CAM degraded with a T_<1/2> of 17 min while EM kinetics corresponded to a T_<1/2> of 3s. Therefore, CAM was 340-fold more stable in pH 1.39 and markedly more stable in the acidic solution than EM.
公益社団法人日本薬学会の論文
1992-03-25