IUCr journals

Ammonium 1-hydroxy-2-(2-pyridinio)ethane-1,1-diyldiphosphonate dihydrate and potassium 1-hydroxy-2-(2-pyridinio)ethane-1,1-diyldiphosphonate dihydrate

Acta Cryst. (2006). C62, m112–m115 [doi: 10.1107/S0108270106002782]

[Potassium risedronate]The crystal packing of potassium risedronate viewed along the c axis, showing the layers of seven-coordinated potassium ions connected by hydrogen bonding.
Risedronic acid is nowadays one of the preferred active substances used for the treatment of osteoporosis. However, the currently used sodium salt of risedronic acid displays different degrees of hydration giving rise to formulation problems. The potassium as well as the ammonium salt, on the other hand, reproducibly forms dihydrates, which are both well defined and very stable. In potassium risedronate, the potassium ions are 7-coordinated in layers connected by hydrogen bonding, while ammonium risedronate molecules form a three-dimensional hydrogen-bonding network.

K. Stahl, J. Oddershede, H. Preikschat, E. Fischer and J. S. Bennekou