title: A novel method of preparing PLGA microcapsules utilizing methylethyl ketone.
abstract: OBJECTIVE
  To substitute dichloromethane with a safer solvent, a solvent extraction process using methylethyl ketone (MEK) was developed to prepare poly(d,l-lactide-co-glycolide) microcapsules.
  
  
  METHODS
  The MEK dispersed phase containing PLGA and progesterone was emulsified in the MEK-saturated aqueous phase (W1) to make a transient oil-in-water (O/W1) emulsion. It was then transferred to a sufficient amount of water (W2) so that MEK residing in polymeric droplets could be extracted effectively into the continuous phase.
  
  
  RESULTS
  This solvent extraction process provided the encapsulation efficiency for progesterone ranging from 77 to 60%. The amount of MEK predissolved in W1, as well as the degree of progesterone payload, influenced the encapsulation efficiency. The leaching profile of MEK analyzed by GC substantiated that, upon dispersion of O/W1, to W2, MEK quickly diffused into the continuous phase. Such a rapid diffusion of MEK from and the ingression of water into polymeric droplets produced hollow microcapsules, as evidenced by their SEM micrographs.
  
  
  CONCLUSIONS
  When solvent extraction/evaporation techniques are employed for preparing PLGA microcapsules, water-immiscibility of a dispersed phase is not an absolute prerequisite to the successful microencapsulation. Adjustment of an initial extraction rate of MEK and formation of a primary transient O/W1 emulsion are found to be very crucial not only for the success of microencapsulation but also for the determination of microcapsule morphology.
authors.affiliation: Pharmaceutical R&D, Merck & Co., Inc., West Point, Pennsylvania 19486, USA.
authors.forename: H
authors.initials: H
authors.lastname: Sah
authors.forename: M S
authors.initials: MS
authors.lastname: Smith
authors.forename: R T
authors.initials: RT
authors.lastname: Chern
mesh_terms: D002074:Butanones / Q000737:chemistry*; D002626:Chemistry, Pharmaceutical / Q000379:methods*; D004339:Drug Compounding; D019344:Lactic Acid; D008752:Methylene Chloride / Q000737:chemistry; D011100:Polyglycolic Acid; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011108:Polymers / Q000737:chemistry*; D012997:Solvents
chemical_list: D002074:Butanones; D011108:Polymers; D012997:Solvents; D000077182:Polylactic Acid-Polyglycolic Acid Copolymer; D011100:Polyglycolic Acid; D019344:Lactic Acid; D008752:Methylene Chloride; C005222:methylethyl ketone