Early adverse events after the first administration of zoledronic acid in Japanese patients with osteoporosis.

Introduction The occurrence of early adverse events and the factors associated with these events in zoledronic acid-treated Japanese patients with osteoporosis were investigated. Materials and methods All patients treated with zoledronic acid for the first time for primary osteoporosis were analyzed. Based on the history of bisphosphonate (BP) administration, the patients were divided into three groups: BP-switch, BP-washout, and naive groups. The BP-washout and naive groups were combined into a non-BP group. Results A total of 184 patients with a mean age of 77.4 years were included. Acute phase reactions (APRs) occurred in 32 patients (17.4%). The significant risk factors were hospitalization (vs. outpatients), BP-switch (vs. non-BP), and age > 80 years (vs. ≤ 69 years), and the odds ratios were 5.63, 0.12, and 0.23, respectively. The serum calcium levels were significantly reduced in the non-BP group, regardless of the co-administration of active vitamin D3. However, the patients who were co-administered active vitamin D3 had significantly higher values than those who were not. In the BP-switch group, no significant reduction in serum calcium levels was observed; however, the reductions tended to be smaller in the patients who were co-administered active vitamin D3. Conclusion Occurrence of APRs might be lesser in clinical practice than in phase 3 clinical trials. Although serum calcium levels decreased in many cases, the decrease could be suppressed by the co-administration of active vitamin D3.