Treatment and prevention of vitamin D insufficiency in cystic fibrosis patients: comparative efficacy of ergocalciferol, cholecalciferol, and UV light

Abstract

Background: The optimal treatment for correcting or preventing vitamin D insufficiency in cystic fibrosis (CF) patients has not been established.

Objective: The aim of the study was to assess the relative efficacy of three modes of vitamin D therapy: cholecalciferol (D3), ergocalciferol (D2), and UV light in raising or maintaining 25(OH)D levels above 30 ng/ml.

Design: Thirty adult CF subjects with vitamin D insufficiency were randomized into one of three treatment arms: D3, D2, or UV light. Subjects randomized to D3 or D2 ingested 50,000 IU of vitamin D weekly, and those randomized to UV exposed their skin to UV light from a lamp five times a week. Serum was collected for 25(OH)D and PTH at baseline and at 12 wk.

Results: Treatment with D3 and D2 raised 25(OH)D levels significantly, from a mean of 21.2 +/- 10.18 to 47.1 +/- 20.5 ng/ml (P < 0.001) and 24.4 +/- 10.3 to 32.7+/- 9.7 ng/ml (P = 0.01), with 100% and 60% reaching 25(OH)D levels above 30 ng/ml, respectively. Treatment with UV did not raise 25(OH)D levels significantly; however, only 55% of subjects were adherent with UV therapy.

Conclusion: This study demonstrates that CF subjects are able to achieve or maintain optimal vitamin D status (>30 ng/ml) with two oral regimens of either D3 or D2 treatment, the former being more efficacious. A confounding variable for this observation is the fact that the D3 and D2 capsules contained different carriers, powder-based vs. oil-based, respectively. UV therapy did not alter vitamin D status, possibly due to poor adherence to UV therapy.

Figure 1

Change in total 25(OH)D, 25(OH)D₃, and 25(OH)D₂ by treatment group. Bold line indicates predicted value for the group using PROC MIXED for mixed linear models and controls for initial levels. Dashed lines represent individual change. The total 25(OH)D concentrations were significantly higher in subjects receiving D₃ and D₂, but not in subjects receiving UV (A). The 25(OH)D₃ concentrations were significantly higher in subjects receiving D₃ and significantly lower in subjects receiving D₂. There were no significant changes in 25(OH)D₃ concentrations in those receiving UV (B). The 25(OH)D₂ concentrations were significantly higher in subjects receiving D₂, and not in subjects receiving D₃ or UV (C).

Figure 2

Change in serum PTH concentrations in response to treatment with ergocalciferol 50,0000 IU once a week for 12 wk (D₂), cholecalciferol 50,000 IU once a week for 12 wk (D₃), or UV light with a Sperti lamp five times a week for 12 wk (UV). Change in PTH were controlled for initial PTH level. Mean change was calculated using least squared means. Subjects receiving both D₂ and D₃ had significantly reduced PTH levels (P = 0.01 and P = 0.05, respectively). There was no significant difference in the change in PTH between the two oral vitamin D treatment groups, D₂ and D₃ (P = 0.86).