PRODUCTION OF AZITHROMYCIN DIHYDRATE

PROBLEM TO BE SOLVED: To obtain an azithromycin dihydrate thermodynamically stable and useful as a medicine in a high yield by adding a base to an aqueous solution of azithromycin using a specific solvent. SOLUTION: This azithromycin dihydrate is obtained by adding a base (preferably sodium hydroxide) to an aqueous solution of azithromycin having a pH of 1-5 and containing acetone. Preferably, the aqueous solution is formed by dissolving azithromycin in acidified water (preferably water adjusted with dilute aqueous solution of hydrochloric acid) having a pH of 1-5 and adding acetone. Preferably, the aqueous solution contains water of 3-7 volume times of a weight of azithromycin. Preferably, the weight ratio of (acetone/water) in the aqueous solution is (7/3)-(3/7). A suspension in the reagent of the resultant crystallized azithromycin is stirred at a temp. of 0-25 deg.C for 6-30 hrs to obtain the objective azithromycin dihydrate having high purity in a high yield.