A process for preparing solid microparticles having an average size ranging from 0.1 to 40µM of hyaluronic acid or an inorganic salt thereof having encased therein protein or peptide drugs such as herein described, the process comprising the steps of : (1) preparing an aqueous solution containing the protein or peptide drug and hyaluronic acid or an inorganic salt thereof under conventional conditions and (2) spray drying or freeze drying the aqueous solution of step (1) under conventional conditions, to obtain the microparticles.
