Evaluating Vitamin D Repletion Regimens and Effects in Veteran Patients

BACKGROUND: There are wide variations in recommended dosing for vitamin D repletion. The identification of specific dosing thresholds to optimize repletion of 25-hydroxyvitamin D3 (also known as 25(OH)D) may help narrow the wide spectrum of vitamin D dosing. OBJECTIVE: The primary objective of this study was to evaluate vitamin D treatment regimens and their dose response effect on vitamin D serum levels. Secondary outcomes include evaluation of the frequency of monitoring vitamin D serum levels and prescription adherence. METHODS: This was a multicenter, retrospective data extraction analysis conducted in patients who initiated monotherapy of ergocalciferol and cholecalciferol between January 1, 2005 and December 31, 2010. Following vitamin D therapy initiation, changes in laboratory values, frequency of laboratory monitoring, and prescription adherence were assessed. Ergocalciferol and cholecalciferol groups were separately organized into quartiles to identify dosing ranges that had the most impact on changes in 25(OH)D laboratory values. RESULTS: There were 2272 and 4140 monotherapy patients in the ergocalciferol and cholecalciferol groups, respectively. Cholecalciferol mean doses between 600 and 1100 IU had similar changes in 25(OH)D ranging from 8 to 9.1 ng/mL. Cholecalciferol mean doses of 2700 IU had 12.7 ng/mL 25(OH)D increase (P < 0.05). Ergocalciferol at mean doses of 11 000 IU had a 19.9 ng/mL increase of 25(OH)D (P < 0.05). At baseline 25(OH)D levels less than 15 ng/mL, 90% of subjects reached a therapeutic 25(OH)D level with a cumulative 300 000 IU cholecalciferol dose. Adherence, calculated by medication possession ratio, was greater with cholecalciferol than ergocalciferol (87% compared with 68%). CONCLUSIONS: Lower vitamin D dose ranges had a comparable effect on 25(OH)D change. Higher doses can produce higher levels, but the relationship is not linear.