Acute phase reactions after zoledronic acid infusion: protective role of 25-OH vitamin D and previous oral bisphosphonate therapy

The most common adverse reaction to zoledronic acid (ZOL) infusion is the acutephase reaction (APR), characterized by transient, usually mild, flu-like symptoms. Previous treatment with oral aminobisphosphonates (BPs) was reported as an independent protective factor for APR, and an association between APR and 25-hydroxyvitamin D (25[OH]D) levels in BP-naïve patients treated with ZOL was identified. The aim of our study was to confirm this association and to see if the association was different in patients previously treated with oral BPs compared with BP-naïve patients, and to investigate the role of 25(OH)D for the time of APR onset.