Calcium complexes of xanthine derivatives: a new aspect of the mode of action of haemorheologically active drugs.

External Ca2+-ions as well as certain xanthine derivatives are known to influence red blood cell properties. Therefore interaction of some xanthine derivatives with Ca-salts have been examined in vitro. Synthesis of five Ca-xanthine derivative complexes is described. The ability of complexing Ca2+-ions gives an insight into the probable mode of action of certain xanthine drugs.