Background: Intravenous bisphosphonates are widely used for treatment of postmenopausal osteoporosis. They are associated with transient influenza-like symptoms, predominantly after the first zoledronic acid (up to 32 %) or ibandronate (up to 5 %) administration. The experience in clinical practice suggests that the incidence of post-dose symptoms is higher than has been reported in clinical trials. We assessed the safety of annual infusions of zoledronic acid and 3-monthly injections of ibandronate in women with postmenopausal osteoporosis.
Methods: In this retrospective study we analysed safety data from 272 postmenopausal women treated with zoledronic acid (n = 127; mean age 68.6 ± 9.4 years) or intravenous (IV) ibandronate (n = 145; mean age 69.1 ± 9.0 years). Safety data (including occurrence of acute-phase reactions and osteonecrosis of the jaw) were gathered in phone call interviews by using a standardized questionnaire.
Results: The number of patients with adverse events was significantly higher in zoledronic acid as compared to ibandronate-treated patients, primarily because of a larger number of post-dose symptoms after bisphosphonate administrations (54.3 % vs. 33.1 %, p < 0.001). Except for occurrence of fever (more common after zoledronic acid infusion), other influenza-like symptoms (myalgia, arthralgia, headache) appeared in a similar proportion of patients after IV treatment (within 24-36 h). Symptoms lasted for >3 days in approximately 50 % of patients. The incidence of symptoms decreased after subsequent infusions. The rate of influenza-like symptoms was more frequent after zoledronic acid than after IV ibandronate in bisphosphonate-naïve patients but comparable in patients pretreated with oral bisphosphonates. There were no spontaneous reports of osteonecrosis of the jaw, arrhythmia or delayed fracture healing.
Conclusion: Although IV bisphosphonates are generally safe, the occurrence of transient influenza-like symptoms after IV bisphosphonates seems to be more frequent in clinical practice than has been reported in clinical trials.