Therapeutic equivalence and adherence to treatment with ibandronate 150 mg and alendronate 70 mg in postmenopausal women of Concepcion city, Chile.

Abstract

Background: Osteoporosis therapy is associated with a poor adherence. Adherence to therapy can be enhanced by decreasing the frequency and complexity of dosing. Once-weekly alendronate 70 mg and once-monthly ibandronate 150 mg are indicated for the treatment of postmenopausal osteoporosis. Aim: To investigate whether once-monthly ibandronate 150 mg increases lumbar spine and hip neck bone mineral density (BMD) to the same degree as weekly alendronate 70 mg; these two agents were compared in a 12 month prospective and randomized trial. Patients and Methods: The study included Chilean postmenopausal (50-61 years old) women from the Bio-Bio Region, mean lumbar spine (L1-L4) BMD T-score < -1.0 and > -3.5. The patients were randomized to once-weekly alendronate 70 mg (n= 31) or monthly ibandronate 150 mg (n= 30). All women received daily calcium carbonate 1,250 mg and vitamin D3 400 IU during the twelve months of the study. Spine and femoral neck BMD was determined using a Lunar DPX Alpha densitometer. Tolerability was evaluated by adverse experience (AE) reporting. Results: Weekly alendronate 70 mg and monthly ibandronate 150 mg significantly increased spinal BMD by 4.02 and 6.23% respectively. Gains in spine BMD were similar with both treatments (p= 0.095). No significant increases were seen in femoral neck BMD with alendronate 70 mg or ibandronate 150 mg. Both regimens were well tolerated and the incidence of upper gastrointestinal AEs were 5.1% and 5.8% with ibandronate and alendronate respectively. Adherence to therapy was significantly greater with monthly ibandronate (93.3%) than weekly alendronate 70 mg (74%). Conclusions: This study demonstrates that weekly alendronate 70 mg and monthly ibandronate 150 mg provide the same efficacy and safety, but adherence to therapy is better with ibandronate than alendronate, probably due to a longer dosing interval.