Acute and long-term effects of zoledronate in adult patients with osteogenesis imperfecta. An observational Spanish study with five years of follow-up.

UNLABELLED: Osteogenesis imperfecta (OI) is an inherited disorder that causes low mineral density and bone fragility. Previous studies have shown the efficacy of bisphosphonates to increase bone mineral density (BMD). This study assessed changes over time in BMD and biochemical markers of bone metabolism in adult patients with osteogenesis imperfecta treated with intravenous zoledronic acid and the safety of this treatment.

PATIENTS AND

METHODS

A prospective, observational study in patients with OI, osteoporosis or osteopenia (T score <-2) who were administered zoledronic acid infusions (4mg IV) every 6 months for three years and annually thereafter. Densitometry was performed annually. Acute changes in complete blood count and calcium, phosphate, and creatinine levels, as well as side effects of the infusion, were recorded 24 and 48h after treatment. Calcium, phosphate, parathyroid hormone (iPTH), 25OH-vitamin D and bone turnover markers (bone alkaline phosphatase, ß-crosslaps and urinary deoxypyridinoline) were measured at baseline and every 12 months. Adverse events and new fractures were recorded.

RESULTS

Twenty patients (6 men and 14 women) were treated. Median follow-up time was five years. Calcium levels and platelet counts significantly decreased 24 and 48hours after the first infusion, and the red blood cell count decreased at 24hours. These changes were not clinically relevant. Seven patients experienced a flu-like episode after the first dose. Treatment induced significant increases in BMD in the lumbar spine (6.7%) after 12 months of follow-up (0.791±0.178 vs. 0.791±0.140g/cm2, p=.003) and at three (5.7%) and five years (9%) of follow-up. Femoral neck BMD significantly increased after 3 years (11.1%): 0.648±0.148 vs. 0.720±0.138g/cm2; p=.01. In total hip, increase in BMD (10.1%) was significant after three years of treatment (0.706±0.118 vs. 0.720±0.138, p=.01). There were no significant differences in calcium and 25OH-vitamin D levels during follow-up, phosphorus significantly decreased after one year, and iPTH increased at three years. ß-crosslaps decreased after one year of treatment. Only one patient sustained new fractures.

CONCLUSIONS

Zoledronic acid is a convenient, safe, and effective treatment that increases BMD in adult patients with OI.