Patent ID: 7229645

Claim:
A process for the preparation of a powder for transdermal particle delivery via needleless injection, which process comprises the step of spray freeze-drying an aqueous solution or suspension via atomising the aqueous solution or suspension into a liquified gas followed by freeze-drying of the liquified gas containing the resulting frozen droplets of the aqueous solution or suspension, wherein said solution or suspension comprises a pharmaceutical agent, and has a solids content of 20% by weight or more, wherein alum is either absent or at a concentration of 30 mg/ml or less, wherein said pharmaceutical agent is selected from the group consisting of a peptide, a hormone, a nucleic acid, a gene construct, an antigen, an antibiotic, an anti-viral agent, an analgesic or analgesic combination, a local or general anaesthetic, and an anti-inflammatory, wherein the drying is conducted in the absence of an organic solvent, wherein said particles have a particle mass mean aerodynamic diameter (MMAD) of from 20 to 70 μm, a particle density of 0.7 to 1.5 g/cm 3 and display a reduction in MMAD of less than 20% in a particle attrition test comprising discharging the said powder via needleless injection into a flask containing a carrier fluid in which the powder is not soluble, and comparing the particle size distribution in the powder before and after needleless injection, and wherein the individual particles of the powder have a substantially spherical aerodynamic shape with a substantially uniform, non-porous surface, have a particle penetration energy suitable for transdermal delivery from a needleless syringe device, and are free-flowing under a dry environment.