Relation between individual and ensemble release kinetics of indomethacin from microspheres.

Indomethacin microspheres based on a combination of ethylcellulose and polyethyleneglycol were prepared using the solvent evaporation process. Release profiles of ensemble and individual microspheres were measured. Both were found to follow first-order kinetics, in contrast to what was expected. This was attributed to the fact that all the particles showed the same kinetic pattern and had a greater degree of homogeneity in the payload, mean particle size and shape, and k1 values than in ensembles of microcapsules.