1. A method of obtaining a lyophilized or frozen preparation of a composition comprising particles containing a drug substance, wherein the particles are coated with PEG, said method comprising adding PVA to an aqueous composition comprising particles, and then lyophilizing or freezing the resulting aqueous composition. A method for preventing aggregation and / or particle size after lyophilization and resuspension, or freezing and thawing of an aqueous composition comprising a drug-containing particle wherein the particles are coated with PEG, said method comprising adding PVA to the aqueous particle composition before lyophilization or freezing. 3. A method according to claim 1 or 2, wherein the concentration of PVA in the aqueous particle composition is in the range from about 0.05% (mass / volume) to about 1% (mass / volume). The method of claim 3, wherein the concentration of PVA in the aqueous particle composition is from about 0.1 to about 0.3%. The method of claim 1 or 2, wherein the molecular weight of the PVA is from about 3 KDa (K) to about 125 KDa (K). The method of claim 5, wherein the molecular weight of the PVA is from about 13 K to about 31 K. A method according to claim 1 or 2, wherein the PVA is hydrolyzed by at least about 50% .8. The method of claim 7, wherein the PVA is hydrolyzed by at least about 75%. The method according to claim 1 or claim 2, wherein the ratio of the mass of PVA to the mass of particles in the final composition leaves less than about 0.2: 1.10. A method according to claim 1 or 2, wherein the concentration of particles in the aqueous particle composition is from about 1% to about 25% (weight / volume). The method of claim 1 or 2, wherein the particles comprise a core, which is a polymeric matrix coated with PEG. The method of claim 1 or 2, wherein the particles include PLA or PLGA. The method of claim 1 or 2, wherein the average particle size in the particle composition does not exceed about 200 nm. The method of claim 1 or 2
