Anhydrous mirtazapine and process for preparing the same

Details Anhydrous mirtazapine and process for preparing the same Anhydrous mirtazapine and process for preparing the same

2001-04-27

2003-12-09

Raymond, Richard L. (Department: 1624)

Drug, bio-affecting and body treating compositions

Designated organic active ingredient containing

Heterocyclic carbon compounds containing a hetero ring...

C540S578000

Reexamination Certificate

active

06660730

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to anhydrous mirtazapine and a process for preparing the same.
2. Discussion of the Background
U.S. Pat. No. 4,062,848 discloses a process for increasing the purity of mirtazapine, (a useful antidepressant), by recrystallizing mirtazapine from a petroleum ether or similar subject.
However, in performing this process, impurities are precipitated in an oily state when crude mirtazapine having a purity of about 95 to 99% is used, so that the crystallization of mirtazapine is inhibited, and makes it difficult to crystallize mirtazapine having a high purity.
Accordingly, there is a significant need for a process capable of efficiently and industrially preparing anhydrous mirtazapine having a high purity from crude mirtazapine.
SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide a process capable of efficiently preparing an anhydrous mirtazapine crystal substantially free of lower alcohol insolubles.
A further object of the present invention is to provide a method for the production of anhydrous mirtazapine having an average particle diameter of 10 to 50 &mgr;m and substantially free of residual solvent.
These and other objects of the present invention have been satisfied by the discovery of a process for preparing an anhydrous mirtazapine crystal, comprising filtering a lower alcohol solution of crude mirtazapine to provide a filtrate; concentrating the filtrate to provide a concentrated filtrate; and crystallizing anhydrous mirtazapine from the concentrated filtrate using a precipitation solvent selected from the group consisting of heptane and petroleum ethers and the anhydrous mirtazapine crystal produced thereby which is substantially free of lower alcohol insolubles.
In a further embodiment, the present invention relates to the discovery of a process for the production of anhydrous mirtazapine crystal that is substantially free of residual solvent, by pulverizing the anhydrous mirtazapine to an average particle diameter of from 10 to 50 &mgr;m, and the anhydrous mirtazapine crystal produced thereby.


REFERENCES:
patent: 4062848 (1977-12-01), Van Der Burg
patent: WO 00/62782 (2000-10-01), None

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