Delayed Release (DR) Risedronate Compared to Immediate Release (IR) in Postmenopausal Women

Study Assessing the Efficacy, Safety, and Pharmacokinetics of 75 and 100 mg Once-a-month Delayed-release Risedronate Formulations Compared to 150 mg Once-a-month Immediate-release Risedronate for 3 Months in Postmenopausal Women Age 45-80

Randomized, multicenter, double-blind, double-dummy, active-controlled, parallel-design study in approximately 201 postmenopausal women. A subset of subjects (approximately 102) will also participate in a pharmacokinetic (PK) component of the study. Each subject will be randomized to 1 of 3 treatment regimens for 3 months.

Inclusion Criteria:

• female, 45 to 80 years of age, in good general health
• postmenopausal ≥2 years, surgically or naturally
• body mass index less than or equal to 32 kg/m^2 at screening

Exclusion Criteria:

• no use within 3 months prior, nor use for more than 1 month at any time within 6 months of: glucocorticoids, anabolic steroids, estrogens, selective estrogen-receptor modulators (SERMs), or estrogen-related drugs, progestins, calcitonin, vitamin D supplements (>1200 IU per day), calcitriol, calcidiol, or alfacalcidol at any dose, any bisphosphonate. fluoride (≥10 mg/day), strontium (≥50 mg/day), parathyroid hormone, investigational bone active agents.
• allergic or abnormal reactions to bisphosphonates
• history of cancer within 5 years, excluding squamous and basal cell carcinoma with 6 month remission
• positive pregnancy test
• no depot injection >10,000 IU vitamin D in previous 9 months.
• no history of GI disease that requires medication, or history of Crohn's disease, ulcerative colitis, diverticular disease, polyps, or surgery that could have changed GI structure or motility.
• no history of frequent diarrhea or constipation that requires regular laxative use.
• no history of alcohol or durg abuse, hyperparathyroidism, cancer previous 5 years, major surgery within 1 month prior to screening, diabetes, uncontrolled hypertension, cardiovascular, hepatic, renal or GI disease.
• no active hyperthyroidism, osteomalacia, use of anticonvulsant medication, or allergic reaction to bisphosphonates