ANHYDROUS MIRTAZAPINE CRYSTALS AND PROCESS FOR THE PRODUCTION THEREOF

摘要

Lowly hygroscopic anhydrous mirtazapine crystals exhibiting a moisture absorption of as low as 0.6 wt. % or below as stored for 500 hours in the ai r under the conditions of 25 ~C, relative humidity of 75 %, and atmospheric pressure; a process for the production thereof; crystals of mirtazapine hydrates represented by formula (I); and a process for the production thereo f (wherein n is an integer of 1 to 5). According to the process, stable anhydrous mirtazapine crystals little exhibiting hygroscopicity can be produced by simple industrial means, and the obtained anhydrous mirtazapine crystals are suitably usable as antidepressant by virtue of their extremely low hygroscopicity.