Since DMSA has two asymmetric carbon atoms, the compound exists as the meso form and the DL form. Meso-DMSA is easier to prepare, more readily available, and has been used in most published investigations. There is a striking difference between the chemical properties of these DMSA forms. Meso-DMSA (m.p. 210-211°C) is sparingly soluble. It must be titrated with alkali to approximately pH 5.5 to go into solution. Alterna*tively, it can be dissolved in 5% NaHC03. The DL form (m.p. 124-125°) is readily soluble in distilled H 20. In the literature and this article, the abbreviation DMSA, unless otherwise stated, denotes the use of the meso form. This author has learned only recently that most of the Chinese studies have involved the synthesis and biological study of the sodium salt of Na- DMSA, not of DMSA per se. In this review no distinction has been made between the two forms.
Solutions of either DMPS or DMSA are remarkably stable for dimer*capto compounds (8), especially at acid pH. Other information about the stability of DMPS has been published but without supporting data (9). For example, it has been claimed that crystalline DMPS retains its antidotal activity and does not decompose when heated for 2 h at 140°C and that aqueous water solutions are stable to prolonged heating. One would suspect, however, that trace amounts of iron and other metals must be absent for stability under such conditions.
, so großen Wert auf das Procain, auch beim DMPS-Test?
