Vitamin D Status and Response to Daily 400 IU Vitamin D3 and Weekly Alendronate 70 mg in Men and Women with Osteoporosis

Abstract

Background Suboptimal vitamin D status is common in elderly individuals. However, the extent of vitamin D inadequacy in men and women being treated for osteoporosis in a family practice setting has not been well characterized. Objective: To describe the distribution of serum 25-hydroxyvitamin D (25-[OH] D) in Canadian men and postmenopausal women with osteoporosis taking 400 IU or less of vitamin D daily and to evaluate the safety, tolerability, and impact of vitamin D3 supplementation 400 IU daily taken concurrently with alendronate sodium 70 mg weekly. Methods: This was a prospective, single-cohort, open-label, multicenter study. Community-dwelling men and postmenopausal women with osteoporosis were recruited at 197 sites across Canada. Patients received vitamin D3 400 IU/day supplementation coadministered with alendronate 70 mg/wk for 16 weeks. The primary outcome was the distribution of serum 25-(OH) D at baseline. Secondary outcome measures included changes from baseline in serum 25-(OH) D levels, adherence to study treatments, and incidence of treatment-related adverse events (AEs). Results: Of the 681 patients included in the analysis, 485 (71.2%) completed the study. Patients were predominantly female (83.1%) with a mean (SD) age of 67.6 (10.7) years. At baseline, mean (SD) serum 25-(OH) D concentration was 25.4 (9.9) ng/mL and 68.0% of the patients had inadequate (less than 30 ng/mL) vitamin D status. At week 16, concentrations increased by 35.1% to 31.2 (9.2) ng/mL (p < 0.001) and the proportion of patients with inadequate 25-(OH) D levels was reduced to 47.0%. Adherence to the treatment regimen was high (greater than 95%). Gastrointestinal disorders were the most frequently reported (6.9%) treatment-related AEs. Conclusions: About two thirds of patients previously diagnosed with osteoporosis have inadequate vitamin D status. A treatment regimen consisting of alendronate 70 mg/wk administered with daily vitamin D3 400 IU supplementation significantly increased patients' serum 25-(OH) D levels, but 47% did not achieve optimal levels. These results support both the National Osteoporosis Foundation and Osteoporosis Canada recommendations for higher vitamin D supplement doses (at least 800 IU daily) in osteoporotic patients receiving pharmacologic therapy for osteoporosis and for monitoring their serum 25-(OH) D response.