METHOD FOR SELECTIVE CRYSTALLIZATION OF IOPROMIDE Z ISOMER

PURPOSE: A crystallizing method for an iopromide Z isomer is provided to selectively crystallize the iopromide Z isomer with a small amount of solvent, and to reduce the crystallizing cost without operating the method for a long time. CONSTITUTION: A selective crystallizing method for an iopromide Z isomer comprises the following steps: dissolving an iopromide E isomer, an iopromide crude crystal, or a their concentrate in alcohol; and obtaining an iopromide crystal by warm processing the dissolved solution from the previous step. A producing method of a composition containing the iopromide Z isomer comprises the following steps: obtaining the iopromide crystal by selectively crystallizing the iopromide Z isomer; and dissolving the crystallized iopromide Z isomer to an aqueous solvent with a pharmaceutically allowable excipient.