title: The effect of oral loading doses of cholecalciferol on the serum concentration of 25-OH-vitamin-D.
abstract: OBJECTIVE
  Severe vitamin D deficiency can be treated with oral loading doses of cholecalciferol. Our objective was to develop an algorithm to accurately calculate the amount of cholecalciferol needed for a loading dose, and what factors should be taken into account.
  
  
  METHODS
  Two studies were conducted on subjects with Vitamin D deficiency. Study 1 was observational, retrospective and included 88 subjects treated with a daily supplementation of cholecalciferol. 60 of these furthermore received a loading dose, calculated by an algorithm.Study 2 was prospective and included 29 subjects treated with a cholecalciferol loading dose, calculated by an algorithm developed based on data from study 1, which included BMI.
  
  
  RESULTS
  Baseline 25OH-vit.D was below 25 nmol/L (study 1) and 23 nmol/L (study 2). Subjects were given a single loading dose of cholecalciferol, averaging 172,000 IU (study 1) and 212,000 IU (study 2), based on their baseline 25OH-vit.D level.25OH-vit.D increased by 35 nmol/L (study 1) and 56 nmol/L (study 2)(range 113.0, SD 29.79) respectively. In study 2 the increase lead to an end 25OH-vit.D of 79 nmol/L--not significantly different from the target value of 80 nmol/L (P=0.46). The increase in 25OH-vit.D in study 1 was significantly lower than in study 2 (P<0.001).
  
  
  CONCLUSIONS
  When calculating loading doses of cholecalciferol, taking subject BMI into account gives a better estimate of the loading dose of vitamin D3 needed to treat vitamin D deficiency. It does not, however, remove the large interindividual variation in dose-response.
authors.affiliation: Department of Endocrinology, Bispebjerg Hospital, University of Copenhagen, Denmark.
authors.forename: Rasmus Bo
authors.initials: RB
authors.lastname: Jansen
authors.affiliation: Department of Endocrinology, Bispebjerg Hospital, University of Copenhagen, Denmark.
authors.forename: Ole Lander
authors.initials: OL
authors.lastname: Svendsen
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D015992:Body Mass Index; D002762:Cholecalciferol / Q000008:administration & dosage*; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012189:Retrospective Studies; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood; D014808:Vitamin D Deficiency / Q000188:drug therapy*
chemical_list: D014807:Vitamin D; D002762:Cholecalciferol; C104450:25-hydroxyvitamin D
keywords: 25-OH-vitamin-D; BMI; loading dose; treatment algorithm; vitamin D