Patent ID: 8106210

Claim:
A process for preparation of high assayed esomeprazole magnesium dihydrate substantially free of its trihydrate form, which comprises: a) (i) adding magnesium chloride or magnesium sulfate to the solution of an alkali metal salt of esomeprazole in an alcoholic solvent; (or) (ii) adding esomeprazole to a solution of magnesium alkoxide in an alcoholic solvent; b) stirring the mass obtained in step (a); c) distilling off the alcoholic solvent from the solution; d) dissolving the residue obtained in step (c) in a chlorinated solvent; e) filtering the solution formed in step (d); f) distilling off the chlorinated solvent from the solution obtained in step (e); g) dissolving the residue obtained in step (f) in a solvent system comprising methanol and water wherein the content of water is 2-6 moles per mole of alkali metal salt of esomeprazole used in step (a)(i) or esomeprazole used in step (a)(ii); and h) precipitating high assayed esomeprazole magnesium dihydrate substantially free of its trihydrate form from the solution obtained in step (g) by adding acetone as an anti-solvent.