PDLLA MICROSPHERES CONTAINING STEROIDS - SPRAY-DRYING, O W AND W/O/W EMULSIFICATIONS AS PREPARATION METHODS/

Hydrocortisone and its more soluble ester, hydrocortisone 21-acetate, have been incorporated into poly(D,L-lactic) acid (PDLLA) microspheres using single, double emulsion/solvent evaporation and by spray-drying techniques. This paper describes the characterization of the micropar ticles obtained (morphology, particle size distribution, drug content, yield of production, in vitro drug release behaviour) and a compariso n of the results (drug loading, drug release, size of the microspheres ) obtained from the different techniques used. These results demonstra te that by using a relatively more soluble ester of an insoluble stero id, hydrocortisone, the drug content within the microspheres can be in creased, together with a high efficiency of loading, irrespective of t he technique employed. In the case of hydrocortisone, spray-drying pro duces the highest loading and encapsulation efficiency compared to bot h single and double emulsion methods for microspheres of similar size (about 2-4 mu m) and suitable for lung delivery, but with lower yields (about 55% versus about 33%).