RESUMO
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 naïve 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.