By Louise Gagnon
MONTREAL -- September 15, 2008 -- The administration of cholecalciferol boosts serum levels of vitamin D in women with osteoporosis, allowing them sufficient vitamin D levels to enter an osteoporosis clinical trial, according to research presented here at the American Society for Bone and Mineral Research (ASBMR) 30th Annual Meeting.
The US Food and Drug Administration has recently modified the lower acceptable limit of 25-hydroxy vitamin D (25-OH vitamin D) for subjects participating in a clinical trial to 60 nmol/L, explained lead investigator Hans Christian Hoeck, MD, PhD, Center for Clinical and Basic Research, Aalborg, Denmark.
Dr. Hoeck and co-investigators enrolled 433 postmenopausal women who were treatment-naïve in an osteoporosis study; at the point of screening, they identified 152 subjects (35.1%) who had 25-OH vitamin D levels <60 nmol/L.
"The objective of the study was to reach the acceptable level of 25-OH vitamin D from the time of screening to inclusion [in] the study," said Dr. Hoeck in an interview at a poster session here on September 14.
Investigators assessed 21 subjects who were ineligible to undergo vitamin D3 supplementation, leaving 131 subjects to receive doses of vitamin D3. Study subjects were administered various dosages per day of 25-OH vitamin D3 for 10 days, including 25, 50, 75, 100, and 200 mcg.
Investigators measured 25-OH vitamin D with an enzyme-linked immunosorbent assay (ELISA) specifically for 25-OH vitamin D3; the assay had no cross reactivity to 25-OH vitamin D2.
After 10 days of supplementation, investigators observed statistically significant increases (P < .001) in the mean value of 25-OH vitamin D in subjects across all 5 dosing arms, but they found that 10 days of treatment did not ensure that all subjects met the threshold limit. Investigators acknowledged that extended treatment beyond 10 days is necessary for all subjects to reach the threshold.
"If we treat subjects with 50 mcg of vitamin D3 for 10 days, followed by 2 weeks treatment with 200 mcg of vitamin D3 daily, it would ensure concentrations of 25-OH [vitamin] D3 greater than 60 nmol/L in all subjects," explained Dr. Hoeck. This regimen would permit patients to reach the necessary 25-OH vitamin D threshold without developing adverse events such as hypercalcaemia, he noted.
Investigators observed no adverse events during the vitamin D supplementation period. They recorded that serum calcium rose within the reference range (P < .006) among subjects taking 25-, 100-, and 200-mcg doses of cholecalciferol. Parathyroid hormone levels only fell in the 25-mcg group (P = .004). Investigators also noted a significant rise in alkaline phosphatase levels in the 50-mcg group (P = .003) and in creatinine levels in the 200-mcg arm (P = .023). There were no variations in AP or creatinine levels observed in any of the other treatment arms (P > .1).
Dr. Hoeck noted that it would be extremely challenging to achieve the revised acceptable limit of 25-OH vitamin D through diet alone.
Funding for this study was provided by Nordic Bioscience A/S.
[Presentation title: The Efficacy and Safety of Short Term Treatment With Different Doses of Cholecalciferol on 25-Hydroxy Vitamin D Levels in Postmenopausal Females With Osteoporosis. Abstract Su434]
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