Risedronate sodium delayed-release tablets (Atelvia): A once-weekly oral bisphosphonate

Osteoporosis is a disease characterized by low bone mass and structural deterioration of bone tissue, leading to bone fragility and an increased susceptibility to fractures, especially of the hip, spine, and wrist. The National Osteoporosis Foundation estimates 44 million Americans, or 55% of the people aged 50 years and older either have or are at high risk for osteoporosis. In October 2010, risedronate sodium delayed-release 35-mg tablets were approved by FDA to treat postmenopausal osteoporosis. Atelvia, like its predecessor Actonel, contains risedronate sodium as its active ingredient, but Atelvia is a delayed-release formulation. Risedronate sodium is a pyridinyl bisphosphonate that acts as an antiresorptive agent by inhibiting osteoclast-mediated bone resorption and modulating bone metabolism.

Efficacy. The efficacy of risedronate sodium delayed-release 35-mg once-a-week tablets in the treatment of postmenopausal osteoporosis was demonstrated in a randomized, double-blind, active-control trial. All patients in this study received supplemental calcium (1,000 mg/day) and vitamin D (800 to 1,000 IU/day). In this trial, risedronate sodium delayed-release 35 mg once-a-week (n=270) administered after breakfast was shown to be noninferior to the previously FDA-approved 5-mg daily dose of risedronate sodium immediate-release (n=261) with a mean difference in lumbar spine bone mineral density (BMD) from baseline between the 2 agents of -0.2% (95% CI, -0.8%–0.3%). Data supporting the efficacy of risedronate sodium delayed-release tablets on reducing fracture rates (33% to 65% relative risk reduction in vertebral fractures, 36% relative risk reduction in nonvertebral fractures) was extrapolated from previous randomized trials of the immediate release formulation.

Safety. The safety of risedronate sodium delayed-release tablets in the treatment of postmenopausal osteoporosis was also assessed in the above randomized trial. The most common adverse reactions associated with risedronate sodium delayed-release tablets in this trial (occurring in >5% of patients) included: diarrhea (8.8%), influenza (7.2%), arthralgia (6.8%), back pain (6.8%), and abdominal pain (5.2%). Hypersensitivity reactions (angioedema, generalized rash, bullous skin reactions), and eye inflammation (iritis, uveitis) have been reported rarely with risedronate sodium delayed-release tablet use. As with other bisphosphonates, osteonecrosis of the jaw has been infrequently observed with risedronate sodium delayed-release tablets.