PROBLEM TO BE SOLVED: To provide an ibandronate crystal polymorphism A which is a pharmaceutically active compound which acts as an efficient bone anti-resorptive drug that directly inhibits osteoclasts activity and also increases bone mass, and which can be used for the treatment and/or prevention of diseases which are associated with bone and calcium metabolic diseases such as, for instance, osteoporosis or Paget's disease.SOLUTION: The present invention relates to a novel polymorph crystal form of 3-(N-methyl-N'-pentyl)amino-1-hydroxypropane-1,1-diphosphonic acid monosodium salt monohydrate (ibandronate) expressed by the following formula (I). An ibandronate polymorph has characteristic peaks expressed in Figure 3.【課題】破骨細胞活性を直接阻害し骨量も高める、有効な骨再吸収抑制剤として作用する薬学的に活性な化合物であり、骨粗鬆症又はパジェット病のような骨及びカルシウム代謝疾患に関連する疾患の治療及び／又は予防に使用することができるイバンドロネート結晶多形Ａの提供。【解決手段】式（Ｉ）で表される３－（Ｎ－メチル－Ｎ’－ペンチル）アミノ－１－ヒドロキシプロパン－１，１－ジホスホン酸一ナトリウム塩一水和物（イバンドロネート）の新規な多形結晶形。図３で示す特性ピークを有するイバンドロネート結晶多形。【選択図】図３
