TORONTO — Women with postmenopausal osteoporosis who had previously discontinued oral bisphosphonate therapy because of gastrointestinal intolerance preferred an intravenous, every-3-month regimen of ibandronate over a monthly oral regimen, Dr. E. Michael Lewiecki said at a world congress on osteoporosis.
Complex dosing instructions designed to maximize bioavailability and address tolerability concerns may affect adherence to oral bisphosphonate therapy, and adherence is crucial to clinical efficacy and fracture prevention, he noted.
Adherence was addressed in a 12-month, open-label multicenter study that included 542 patients with osteoporosis or osteopenia who had stopped daily or weekly treatment with oral alendronate or risedronate because of symptoms such as heartburn and acid reflux. All got supplemental vitamin D (400 IU/day) and elemental calcium (1,000 mg/day). Patients were given the choice of oral ibandronate, 150 mg once monthly, or 3 mg intravenously every 3 months. The intravenous injection takes 15 to 30 seconds to complete. A total of 396 (73%) of patients chose the intravenous regimen, and 146 (27%) chose the oral route. They were permitted to switch treatment groups once during the study if they experienced adverse effects.
Severity and frequency of gastrointestinal symptoms and other side effects were evaluated with surveys administered at baseline and at months 1, 4, 7, and 10.
Available data indicate that adherence to both regimens at 6 months was high, at 94.5%. Actual duration of study medication intake divided by maximum duration of intake and a threshold of 75% or more was used to define adherence, according to Dr. Lewiecki of New Mexico Clinical Research and Osteoporosis Center, Albuquerque.
Among patients receiving the oral drug, adherence was 87.7%, while adherence was 94.9% among those receiving the intravenous formulation, Dr. Lewiecki wrote in a poster session at the meeting, which was sponsored by the International Osteoporosis Foundation.
In patients who chose the intravenous route of administration, 147 (37.1%) had a history of fracture as an adult, compared with 36 (24.7%) of those who chose the oral drug.
So far, 26 patients have switched their route of administration. Eleven switched from oral to intravenous ibandronate because of gastrointestinal intolerance; 15 went from intravenous to oral for reasons including influenzalike symptoms and injection-site reactions. By month 4, 28.1% and 36.6% of patients on the oral and intravenous drugs, respectively, reported improvements in gastrointestinal tolerance compared with baseline.
“Patients who had previously discontinued weekly or daily oral bisphosphonates because of gastrointestinal intolerance [seem to] prefer intravenous dosing, and patients with a previous fracture are even more likely to do so than patients without a previous fracture,” Dr. Lewiecki said. The study was sponsored by Roche Laboratories. Dr. Lewiecki made no disclosures.