PDLLA microspheres containing steroids: Spray-drying, o/w and w/o/w emulsifications as preparation methods

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Abstract
Hydrocortisone and its more soluble ester, hydrocortisone 21-a-cetate, 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 microparticles obtained (morphology, particle size distribution, drug content, yield of production, in vitro drug release behaviour) and a comparison of the results (drug loading, drug release, size of the microspheres) obtained from the different techniques used. These results demonstrate that by using a relatively more soluble ester of an insoluble steroid, hydrocortisone, the drug content within the microspheres can be increased, together with a high efficiency of loading, irrespective of the technique employed. In the case of hydrocortisone, spray-drying produces the highest loading and encapsulation eficiency compared to both single and double emulsion methods for microspheres of similar size (about 2–4—m) and suitable for lung delivery, but with lower yields (about 55% versus about 33%).