Background Zoledronic acid is an intravenous bisphosphonate used in osteoporosis and Paget’s disease of bone. It is usually well tolerated, although it may cause some side effects.

Objectives To describe the clinical characteristics, indications, side effects and densitometric parameters in patients treated with zoledronic acid.

Methods Retrospective study (2006-2012) at two hospitals with a referral area of 900.000 people. We reviewed the medical records of patients treated with zoledronic acid. We collected the epidemiological and clinical features and side effects. We conducted a telephone interview to complete the missed data.

Results Two hundred and four patients received zoledronic acid: 146 women (71.6%) and 58 men (28.4%), with mean age of 70.5 years (range: 38-89 years). The medical indication for the administration was: 149 osteoporosis, 46 Paget’s disease of bone and 8 other bone diseases (5 SAPHO syndrome, 2 Brittle bone’s disease and 1 progressive multifocal osteitis). The causes of osteoporosis were: postmenopausal 93 (62.4%), secondary 42 (28.2%) - most of them due to glucocorticoid treatment -, and male osteoporosis 14 (9.4%).

Seventy-three percent of the patients with osteoporosis had received other treatments previously (73.6% oral bisphosphonates, 27.3% teriparatide or PTH 1-84, 22.7% intravenous ibandronate, 18.1% strontium ranelate, 10% calcitonin, 9% raloxifene and 7.3% pamidronate). Ninety-seven patients (65.1%) had fractures before treatment: vertebral (82%), rib (12.3%), wrist (9.2%), femur (8.2%), other (12.3%) - isquiopubian branches, foot, elbow, humerus, phalanges. Only 14 patients (9.4%) had fractures after treatment. The average of bone mineral density before treatment was: T score -3.1 in the lumbar spine (L2-L4) and -2.4 in the femur.

Of all patients, 110 (73.8%) had received a single infusion, 46 (30.9%) 2 infusions, 38 (25.5%) 3 infusions and 10 (6.7%) 4 infusions of zoledronic acid.

Thirty-nine patients had side effects (19.1%): 26 men and 13 women, with a mean age of 66.4 years. Twenty-three of these patients were treated because of having osteoporosis, 15 Paget’s disease of bone and one osteogenesis imperfecta. The most described side effects were: flu-like syndrome (69%), arthralgia (7.7%), uveitis (5.1%) and arthritis, kidney failure, hypertensive crisis, rash, epistaxis, fatigue and ventricular arrhythmia (2.6 % each).

We used chi-square test with Yates correction to compare the incidence of side effects in patients with osteoporosis to patients with Paget’s disease of bone. We obtained a value of 5.56 with statistical significance (p = 0.01) for Paget’s disease of bone.

Conclusions The most common indication for administration of intravenous zoledronic acid is postmenopausal osteoporosis. A high percentage of patients had previously received different treatments and had fractures before treatment. Nearly 20% of patients have side effects and the most common is a flu-like syndrome. Patients treated for Paget’s disease of bone have a higher incidence of side effects than those treated for osteoporosis (p = 0.01).

Disclosure of Interest None Declared