BACKGROUND: Data on the rate of
concomitant vitamin D use with antiresorptive
medications are limited. Such information is important because
vitamin D is indicated in patients with
osteoporosis, including those receiving
bisphosphonates, and there is evidence of inadequate
use by these patients. OBJECTIVE: To examine prescription
vitamin D utilization patterns. RESEARCH DESIGN AND METHODS: A retrospective analysis of patients
aged >/= 65 years was conducted in a Canadian pharmacy-insurance organization (RAMQ) who received at least one prescription for an antiresorptive agent (i.e.,
alendronate,
risedronate,
raloxifene) from January 1, 1996, through December 31, 2003, and did not switch to any other agent during the 1-year post period. Data on prescriptions of
vitamin D formulations on the RAMQ formulary (e.g., alfacalcidol,
calcitriol,
cholecalciferol, doxercalciferol,
ergocalciferol) were also captured. No data on generic or over-the-counter
vitamin D preparations were available. A
vitamin D and antiresorptive agent possession ratio (R(P)) was computed as: R(P) = SigmaD(SPVD) / SigmaD(SARR) where SigmaD(SPVD) = the sum of the days of supply with prescription
vitamin D and SigmaD(SARR) = the sum of days of supply with
alendronate,
risedronate, or
raloxifene A
vitamin D and antiresorptive agent overlap ratio (R(0)) was computed as: R(0) = SigmaD(SPVDOARR) / SigmaD(SARR) where SigmaD(SPVDOARR) = the sum of days of supply of prescription
vitamin D overlapping with
alendronate,
risedronate, or
raloxifene, and SigmaD(SARR) = the sum of the days of supply with
alendronate,
risedronate, or
raloxifene. RESULTS: A total of 46 226 antiresorptive treatment users were identified, > 90% of whom were women. A total of 17 151 (37.1%) had
concomitant vitamin D prescriptions. The
average duration of prescription therapy with
alendronate,
risedronate, or
raloxifene was 247 days; and the
mean duration of prescription
vitamin D therapy was 83 days. Patients had a supply of
vitamin D for 55% of days of antiresorptive agents therapy (R(P) = 0.55) and a
vitamin D supply overlapping with 24% of their days on antiresorptive agents (R(o) = 0.24). Possession and overlap ratios were significantly higher in patients receiving once-weekly
bisphosphonate prescriptions compared with once-daily regimens (
bisphosphonates or
raloxifene).
Vitamin D prescriptions were also significantly more likely in patients receiving prescriptions for once-weekly
bisphosphonates (
odds ratio (OR) = 4.65; 95% CI = 4.29-5.05; p < 0.0001) and once-daily
bisphosphonates (OR = 1.91; 95% CI = 1.76-2.07; p < 0.0001) compared with once-daily
raloxifene. CONCLUSIONS: Despite the benefits of
vitamin D for
osteoporosis, most patients ( approximately 63%) receiving prescriptions for antiresorptive agents were not taking
vitamin D, indicating a substantial treatment gap. The study is limited by including data only on (1)
pharmacy claims, which do not equate to patient behaviors, such as filling or refilling prescriptions and/or taking the
medications; and (2) prescription (but not generic or over-the-counter)
vitamin D formulations.
