Structural and thermal characterization of sodium ibandronate monohydrate

Sodium Ibandronate (NaIb) belongs to the nitrogen-containing bisphosphonates drugs, used as anti-resorptive medications for the treatment of osteoporosis. The crystalline form of NaIb monohydrate was observed to undergo reversible thermal dehydration and rehydration, according to its hygroscopic nature and to the arrangement of the water molecules in the crystal lattice. Dehydration and rehydration were observed and confirmed by variable temperature X-ray diffraction on the basis of the DSC pattern and TG analysis that shows, by heating the sample from 40 to 200 °C, a loss of 5% weight corresponding to a water molecule loss. The water loss causes a phase transition to a more dense phase that can be rehydrated if it is left in a humid environment. The solid state characterization of NaIb monohydrate has been performed by X-ray single crystal diffraction analysis. The NaIb crystallizes as monohydrate salt in the triclinic system, space group P-1, with Z = 2, a = 5.973(1) Å, b = 9.193(1) Å, c = 14.830(2) Å, ? = 98.22(1)°, ? = 98.97(1)°, ? = 93.74(1)°, V = 792.9(2) Å 3. Each anionic group exist as zwitterionic entity with a total charge of -1. In the crystal packing, the octahedral coordination around the Na cations determines a centrosymmetric double chains structure elongated into the [100] direction. The water molecules are located inside the inter-chains cavities.