Drug companies use a range of salts to produce crystalline derivatives suitable for processing

28 February 2003

Care must be taken with these salts since they may be unstable, since the free base can attack the fumarate or maleate to give adducts. For example, the Ciba Geigy compound CGP 15210 contained an impurity which could not be removed by recrystallisation (300g scale) — instead the impurity INCREASED, owing to Michael addition of the amine to the fumarate

This reference comes from an excellent book , Handbook of Pharmaceutical Salts, PH Stahl and GG Wermuth, Wiley VCH, 2002 (price £85 ISBN 3-906390-26-8) which will shortly be reviewed in OPRD.

For other references to additions to fumarates and maleates see:

PGE-7762928; M Gazda et al Pharm. Sci., 1998, 1, 5-403.

Seproxetine Maleate hemihydrate; SA Schildcrout et al Drug Dev Ind Pharm 1993, 19, 1113