A review of minodronic acid hydrate for the treatment of osteoporosis

Minodronic acid hydrate was the first bisphosphonate developed and approved for osteoporosis treatment in Japan. With regard to inhibition of bone resorption, minodronic acid hydrate is 1000 times more effective than etidronic acid and 10–100 times more effective than alendronic acid. Clinical trials conducted to date have focused on postmenopausal female patients suffering from primary osteoporosis. In these trials, 1 mg of oral minodronic acid hydrate was administrated once daily, and a significant increase was observed in lumbar-spine and hip-joint bone density 1–2 years after administration. All markers of bone metabolism urinary collagen type 1 cross-linked N-telopeptide, urinary free deoxypyridinoline, serum bone alkaline phosphatase, and serum osteocalcin were decreased. The incidence rate of new vertebral and nonvertebral fractures was also decreased. Therefore, effectiveness in fracture prevention was confirmed. A form of minodronic acid (50 mg) requiring once-monthly administration has been developed and is currently being used clinically. A comparative study between this new formulation and once-daily minodronic acid (1 mg) showed no significant differences between the two formulations in terms of improvement rates in lumbar-spine and hip-joint bone density, changes in bone metabolism markers, or incidence of side effects. This indicates the noninferiority of the monthly formulation. Side effects such as osteonecrosis of the jaw or atypical femoral fractures were not reported with other bisphosphonates, although it is believed that these side effects may emerge as future studies continue to be conducted. On the basis of studies conducted to date, minodronic acid hydrate is considered effective for improving bone density and preventing fractures. We anticipate further investigations in the future.