title: How well are the optimal serum 25OHD concentrations reached in high-dose intermittent vitamin D therapy? a placebo-controlled study on comparison between 100 000 IU and 200 000 IU of oral D3 every 3 months in elderly women.
abstract: OBJECTIVE
  Intermittent dosing may improve adherence to vitamin D therapy. Dosing regimen should maintain optimal serum 25-hydroxyvitamin D (25OHD) levels over all the year. We compared two dosing regimens, the primary outcome being the percentage of 25OHD measurements reaching the targets of 75 nmol/l or 50 nmol/l after baseline.
  
  
  METHODS
  Randomized, placebo-controlled parallel group comparison.
  
  
  METHODS
  Sixty women aged 75·0 ± 2·9 years.
  
  
  METHODS
  100 000 IU (group 1D) or 200 000 IU (2D) of vitamin D3 or placebo orally every 3 months plus calcium 1 g daily for 1 year.
  
  
  METHODS
  Serum 25OHD, 1,25-dihydroxyvitamin D, PTH, sclerostin, ionized calcium, urinary calcium, renal function, bone turnover markers.
  
  
  RESULTS
  Serum 25OHD increased, but the difference between two doses was of borderline significance (P = 0·0554; area under curve analysis). Immediate postadministrative increases were higher in the 2D vs 1D group (P < 0·05) after 3 and 6 months' dosing. In the 1D and 2D groups, 51·2% and 57·7% of all on-treatment measurements reached the target of 75 nmol/l. PTH levels differed marginally (P = 0·0759) due to tendency to lowering immediately after vitamin D boluses. Urinary calcium differed between the groups (P = 0·0193) due to increases 1 week after vitamin D dosing.
  
  
  CONCLUSIONS
  The doses of 100 000 or 200 000 IU of oral cholecalciferol every 3 months were not capable of stabilizing 25OHD levels over the target of 75 nmol/l over the year. To improve the efficacy of high-dose vitamin D therapy, the interval between boluses has to be shortened instead of increasing their size.
authors.affiliation: Department of Orthopaedics and Traumatology, Helsinki University Central Hospital and University of Helsinki, Jorvi Hospital, Espoo, Finland.
authors.forename: Ville-Valtteri
authors.initials: VV
authors.lastname: Välimäki
authors.affiliation: Department of Biostatistics, University of Turku, Turku, Finland.
authors.forename: Eliisa
authors.initials: E
authors.lastname: Löyttyniemi
authors.affiliation: Abdominal Center, Helsinki University Central Hospital, Peijas Hospital, Vantaa, Finland.
authors.forename: Tuula
authors.initials: T
authors.lastname: Pekkarinen
authors.affiliation: Division of Endocrinology, Department of Medicine, Helsinki University Central Hospital, Helsinki, Finland.
authors.forename: Matti J
authors.initials: MJ
authors.lastname: Välimäki
mesh_terms: D000368:Aged; D002118:Calcium / Q000008:administration & dosage / Q000652:urine; D002762:Cholecalciferol / Q000008:administration & dosage* / Q000627:therapeutic use; D019587:Dietary Supplements; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D014807:Vitamin D / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D014807:Vitamin D; D002762:Cholecalciferol; C097949:1,25-dihydroxyvitamin D; C104450:25-hydroxyvitamin D; D002118:Calcium