Risedronate once monthly: a potential new regimen for the treatment of postmenopausal osteoporosis.

Postmenopausal osteoporosis increases susceptibility to low-trauma fractures due to reduced bone volume and microarchitectural deterioration. Daily nitrogen-containing bisphosphonates have shown antifracture efficacy in many studies and are the most commonly prescribed treatment for women with postmenopausal osteoporosis. However, optimal efficacy is often not achieved due to poor patient adherence to medication. Current dosing schedules are often inconvenient or impractical for patients. Poor adherence increases risk of fracture, which itself increases morbidity, healthcare costs and, potentially, mortality. Although weekly rather than daily dosing of bisphosphonates has improved adherence, significant problems remain. Efforts to reduce dosing frequency as a possible means for further improving adherence (compliance and persistence), and therefore treatment outcomes, are ongoing. Risedronate, a third-generation bisphosphonate, has been shown in multiple clinical trials to reduce fracture risk and improve bone mineral density in postmenopausal women with osteoporosis. Risedronate has a specific structure and set of characteristics that enable less frequent dosing. This paper reviews the structure of risedronate, and how this translates into high antiresorptive potency, favorable bone binding, persistence in bone, and good tolerability that permits less frequent dosing. The paper also reviews the clinical evidence for risedronate, demonstrating the viability of less frequent dosing, with its potential benefits for patient convenience and adherence to therapy. Two equivalence or non-inferiority bridging studies have demonstrated the option of novel risedronate dosing regimens. These studies are reviewed to demonstrate the efficacy and safety of two different monthly regimens of risedronate in the treatment of postmenopausal osteoporosis: 75 mg on 2 consecutive days a month and 150 mg once a month. Data for oral risedronate 150 mg once a month are limited to 1 year's treatment duration. In previous clinical trials, patients receiving risedronate 5 mg daily have been followed for up to 7 years, with no evidence of loss of effectiveness. Risedronate 150 mg once a month has a comparable efficacy and safety to daily doses in the treatment of postmenopausal osteoporosis. These additional treatment options with risedronate provide easier dosing alternatives for patients.