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

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