Double Emulsion –solvent extraction
An aqueous solution of the peptide (which may contain excipients such as gelatin) is first emulsified in a polymer vehicle where the polyesters have been solubilized in an organic solvent (generally dichloromethane or ethyl acetate). This first emulsion is then poured into a second continuous aqueous phase containing a surfactant such as polyvinyl alcohol (PVA) from where the solvent will be extracted leading to the concomitant solidification of the microspheres.
Process limitations: Minimal solubility of the peptide in the organic solvent; shear stresses; the presence of residual solvent; the necessity of the aseptic process.
Example of manufactured product: Lupron Depot.