Tolerability of the first infusion of once-yearly zoledronic acid within one to two weeks after hip fracture surgery

Objective: Once-yearly infusions of zoledronic acid (ZA) 5 mg may be optimal for secondary fracture prevention after hip fracture (HF), but there are crucial side effects of ZA. This study assessed the tolerability of the first infusion of once-yearly ZA within one to two weeks after HF surgery and to identify risk factors for acute-phase reactions (APRs) and the decrease in serum calcium (Ca) concentration. Methods: We analyzed 84 patients (average age: 83 years, 18 men and 66 women) who met the inclusion criteria. The patients underwent the first infusion of ZA one to two weeks after HF surgery and received antipyretic analgesics and active vitamin D analog. Results: APRs occurred in ten patients (11.9%) and all these patients had pyrexia (>37.5 degrees C) and/or other symptoms. The asymptomatic hypocalcemia (serum Ca < 8.3 mg/dL) incidence was 6.0% at 7 days after ZA infusion. Compared with female patients without APRs, female patients with APRs had significantly higher levels of serum 25-dihydroxyvitamin D at baseline and serum C-reactive protein on the day ZA was administered (day 0). Multiple linear regression analyses showed that serum level of tartrate-resistant acid phosphatase-5b were significantly associated with an absolute decrease in serum corrected Ca from day 0 to day 7. Conclusions: The first infusion of ZA within one to two weeks after HF surgery was well tolerated with the combined use of antipyretic analgesics and active vitamin D analog. Higher inflammatory condition after surgery which is more likely sensitized by ZA administration may increase the risk of APRs, and high bone turnover may increase hypocalcemia risk.