Randomized, Open, Parallel, Active Controlled Study on Fracture Prevention in Antiosteoporosis Treatment (OF Study)

Inclusion Criteria: Inpatient or outpatient is not asked. If using any anti-osteoporotic agent other than calcium preparations (i.e., contraindicated for concomitant use stipulated in the protocol of this post-marketing study), such agent must be discontinued. Even after the discontinuation, calcium dosing is permitted with a condition that the subsequent use is started after a 8-week elapse from the discontinuation. Patients with primary osteoporosis (diagnosed according to "Diagnostic Criteria for Primary Osteoporosis issued by the Japanese Society for Bone and Mineral Research (1995)." Post-menopausal patients aged 50 years or older. Patients who agree to participate in a 4-year follow-up observation. Patients who provide written informed consent. Exclusion Criteira: Patients on warfarin potassium (Warfarin®) therapy. Patients with hypercalcemia. Patietns with renal calculus. Patients with a known history of hypersensitivity to calcium or menatetrenone preparations. Patients with severe complication in the hepatic, renal, gastrointestinal, cardio- and cerebrovascular system. Patients who underwent bilateral ovariectomy. Patients with radiotherapy in the pelvis or para-aortic area. Patients with the following X-ray findings; Patients showing osteophytes connecting with adjacent vertebral osteophytes Patients showing hyperostosis of ligament around the vertebral body Patients showing inter-body fusion Patients who experienced surgical intervention(s) in the spine Patients with scoliosis which disturbs a diagnosing of vertebral fracture Patients who have been treated with anti-osteoporotic agents, other than calcium preparation, within 8 months prior to the study treatment (but not applied to the following; if discontinued, non-treated, or shifted to calcium monotherapy for 8 weeks or longer before starting the study treatment). Patients who experienced bisphosphonates in the past. Patients who are likely to show insufficient absorption of liposoluble agents such as biliary atresia, impaired bile secretion, etc. Other patients who are judged to be ineligible for study entry by the investigator or investigator.