Method for preparing aqueous emulsion for coating solid pharmaceutical

Abstract

A method permits the easy preparation of an aqueous emulsion for coating solid pharmaceutical preparations through emulsification in water without addition of additives such as emulsifying agents, polymerization initiators, chain transfer agents, salts and plasticizers. A cellulosic polymer is dissolved in an organic solvent miscible in water in any rate or a mixed solvent comprising the organic solvent and water to give a polymer solution. The polymer solution is mixed with water to disperse the solution in water and thereafter the organic solvent is removed to form an aqueous emulsion for coating solid pharmaceutical preparations. If ethyl cellulose is used as a coating base, ethyl cellulose is first dissolved in a non-hydrophilic solvent to give a non-hydrophilic solution thereof. The non-hydrophilic solution is dissolved in a solvent containing at least an organic solvent miscible with water in any rate, the resulting ethyl cellulose solution is brought into contact with water to disperse the ethyl cellulose solution therein and then the solvent is removed from the emulsion formed through self-emulsification of the ethyl cellulose solution to form an aqueous coating emulsion.