Loading of hydrophobic drugs into hydrophilic polymer delivery systems

A process for forming drug-loaded polymer particles comprising the steps:

• a) providing particles comprising a matrix of water-insoluble polymer, which, when neat, are swellable in phosphate buffered saline (PBS) at room temperature to an equilibrium water content in the range of from 40% to 99% by weight based on polymer plus PBS;
• b) providing a solution of a drug having a water solubility of less than 10 g/l at room temperature, in a first organic solvent is selected to be capable of swelling neat particles;
• c) containing the particles with the solution of drug whereby a solution of drug in solvent becomes impregnated into the particles;
• d) separating drug solution which has not impregnated the particles in step c) from the impregnated particles and recovering the impregnated particles;
• e) contacting the impregnated particles with aqueous liquid whereby drug is precipitated in the core of the particles;
• f) providing a volatile, second solvent in which the particles are less swellable, relative to their swellability in water, and which is a solvent for the drug, wherein the drug solubility in the second solvent is at least 0.1 g/l;
• and
• g) rinsing the particles produced in step e) with the second solvent whereby drug on and close to the surface of the particles is removed with the second solvent;
• and, optionally
• h) drying the drug-loaded polymer particles by vacuum, or freeze drying, or air flow to remove the second solvent.