Micronized emulsion for controlled release of physostigmine after oral administration. Part I. Formulation design

Our aim was to incorporate physostigmine in a fine micronized emulsion delivery system which would prolong drug release following oral administration. Investigation of various types of equipment and experimental conditions led to a fine micronized emulsion of mean droplet size around 1 micron, which was stable at pH 5.5. The effect of physostigmine concentration and salt formation on the interfacial tension and zeta potential of the emulsion was studied. Physostigmine base markedly decreased the interfacial tension as compared to physostigmine hemisulfate and salicylate. Zeta potential was highest in the case of the salicylate. After storage at 4 37 degrees C for four months, the emulsion did not undergo any significant change.