Bismuth compounds have been used for over 200 years to treat diseases of the gastrointestinal tract (disinfection and pH regulation). The exact mechanism of Bi pharmaceuticals is still essentially unknown.
Usually basic Bi(III) citrate, Bi(III) nitrate or Bi(III) salicylate are used. In aqueous solution the compounds have a strong tendency to build hydroxo-bridged cage and and polymeric structures.
It is thought that the efficency of the compounds depends on the pH dependent formation of polymer layers. Bi(III) citrate complexes are stable between pH 3.5 - 7.5 but form different structures.