Acute phase response following intravenous zoledronate in postmenopausal women with low bone mass.

An acute phase response (APR) is frequently observed in patients treated with intravenous (i.v.) zoledronate (ZOL). We aimed to define clinical and laboratory parameters that may predict ZOL-induced APR in women with low bone mass. Fifty-one postmenopausal women with low bone mass were given a single i.v. infusion of ZOL 5mg. APR was clinically defined by the visual analog pain scale (VAS) for the musculoskeletal symptoms and body temperature. White blood cell count (WBC), leucocyte subpopulations, C-reactive protein (CRP), parathyroid hormone (PTH), 25-hydroxyvitamin D [25(OH)D], interleukins (IL)-1b and -6, tumor necrosis factor (TNF)α and interferon (IFN)γ were measured before and 48 h following the infusion. Subsequently, patients were divided into those experiencing APR (APR+) or not (APR-). WBC, granulocytes, CRP, IL-1b and IL-6 were significantly increased, whereas lymphocytes, eosinophils, calcium, phosphate and 25(OH)D decreased 48h after ZOL infusion. Twenty-eight of the 51 patients (54.9%) experienced an APR. APR+ patients were younger and had higher baseline lymphocytes compared to APR- patients. There was no difference (p=0.405) in the development of APR between treatment-naive patients (19/32, 59.4%) and patients previously treated with another oral nitrogen-containing bisphosphonate (9/19, 47.4%). In conclusion, our data suggest that pre-treatment higher lymphocyte number increases the risk of APR while previous treatment with another nitrogen-containing bisphosphonate does not significantly reduce the risk. Serum 25(OH)D concentrations decrease significantly after the infusion, possibly as part of the inflammatory response to ZOL.