Method for preparing biodegradable microspheres using stabilized single-phase mixed solution

A method of preparing biodegradable microspheres having uniform drug loading efficiency, comprising the steps of:

• i) dissolving a drug in a mixed solvent in which water and alcohol are mixed in a volume ratio of 1:4 to 1:9 to form a drug solution;
• ii) adding the drug solution obtained in step i) to a non-polar organic solvent in which a biodegradable polymer is dissolved, thus forming a single-phase mixed solution without forming an emulsion;
• iii) dispersing the single-phase mixed solution in an aqueous phase in which a surfactant is dissolved, thus forming a microsphere emulsion;
• iv) evaporating the non-polar organic solvent in the microsphere emulsion formed in step iii), and then hardening the microspheres;
• and
• v) obtaining the microsphere powder by a freeze-drying,
• wherein the alcohol is methanol or ethanol,
• wherein the drug is a water-soluble drug,
• wherein the biodegradable polymer is poly(lactic-co-glycolic acid) or poly(lactic acid),
• wherein the non-polar organic solvent is dichloromethane or chloroform, and
• wherein in step ii), the volume ratio at which the drug solution and the non-polar organic solvent in which the biodegradable polymer is dissolved are mixed is in a range of 1:1 to 1:12.