A novel crystal form the pharmaceutical compound olanzapine, processes for its preparation and its pharmaceutical use are disclosed.

The present invention provides the novel Dihydrate D 2-methyl-thieno-benzodiazepine and a formulation therefor.

Crystalline Form I of 2-methyl-4-(4-methyl-1-piperazinyl)-10H-thieno[2,3-b][1,5]benzodiazepine characterised by x-ray powder diffraction peaks at approximately 9.94, 8.53, 8.19, 6.86, 6.35, 5.47, 4.83, 4.71, 4.53, 4.22, 4.08, 3.82, 3.75, 3.69, 3.50, 3.34, 3.11, 2.94, 2.82, 2.76, 2.59, 2.34, 2.03, 1.92 d (interplanar spacing) values; infrared absorbance bands at approximately 1456, 1365, 905, 757, 662 & 604 cm.sup.-3 and having stable colour at ambient conditions of storage; and the process of its preparation comprising at least two repetitive steps of crystallization from one or more organic solvent by dissolving 2-methyl-4-(4-methyl-1-piperazinyl)-10H-thieno[2,3-b][1,5]benzodiazepine in said solvent and allowing crystallization to occur; wherein in at least one step the solution is purified by treating with a solid adsorbent material and filtering; and wherein in the last step the crystalline material is subjected to drying.

This invention encompasses methods of synthesizing olanzapine without solvents or by using low boiling organic solvents.

Several salts of olanzapine, including olanzapine malonate, olanzapine glycolate, olanzapine maleate, and olanzapine benzoate, have been found to have favorable solid state characteristics.