title: Investigation of the diurnal variation in bone resorption for optimal drug delivery and efficacy in osteoporosis with oral calcitonin.
abstract: BACKGROUND
  Bone resorption displays marked diurnal variation. Reversible inhibition of bone resorption may result in best possible efficacy when bone resorption peaks. The aim of the study was to assess the pharmacokinetic (PK) and pharmacodynamic (PD) profiles of 0.8 mg of oral salmon calcitonin (sCT) and the effect of timing of drug intake.
  
  
  METHODS
  The study was a randomized, double-blind, double-dummy, placebo-controlled, phase I study to assess the pharmacokinetic (PK) and pharmacodynamic (PD) profiles of 0.8 mg of oral sCT in healthy postmenopausal women. Totally 81 subjects were included, aimed at investigation of a morning dose given at 8:00 (n = 42), a pre-dinner dose given at 17:00 (n = 20), and an evening dose given at 22:00 (n = 19). Plasma sCT concentrations and bone resorption (C-terminal-telopeptide of collagen type I (CTX-I)) was assessed.
  
  
  RESULTS
  Morning and pre-dinner dosing led to comparable concentration of sCT of 45 pg/ml, whereas there was a tendency towards lower Cmax for the evening dosing having a mean of 24 pg/ml. The maximum difference from placebo was observed 1 to 3 hours post-dose with a 40 to 50% suppression consequent to morning dose, and about 75% suppression after pre-dinner and evening dose, due to the increase bone resorption as a result of circadian variation.
  
  
  CONCLUSIONS
  The study suggests that orally administered 0.8 mg of salmon calcitonin was effective in suppression of serum CTX irrespective of time of dosing. The pre-dinner dosing resulted in optimum efficacy response corresponding to an overall suppression of bone resorption by 25%.
authors.affiliation: Nordic Bioscience A/S, Herlev/, DK-2730 Herlev, Denmark. mk@nordicbioscience.com
authors.forename: M A
authors.initials: MA
authors.lastname: Karsdal
authors.forename: I
authors.initials: I
authors.lastname: Byrjalsen
authors.forename: B J
authors.initials: BJ
authors.lastname: Riis
authors.forename: C
authors.initials: C
authors.lastname: Christiansen
mesh_terms: D000284:Administration, Oral; D000368:Aged; D001862:Bone Resorption / Q000188:drug therapy / Q000378:metabolism*; D002116:Calcitonin / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000494:pharmacology; D002940:Circadian Rhythm; D004311:Double-Blind Method; D016503:Drug Delivery Systems; D005260:Female; D006801:Humans; D008875:Middle Aged; D010024:Osteoporosis / Q000188:drug therapy / Q000378:metabolism*; D016896:Treatment Outcome
chemical_list: C028815:salmon calcitonin; D002116:Calcitonin