MORNING OR EVENING ADMINISTRATION OF NASAL CALCITONIN - EFFECTS ON BIOCHEMICAL MARKERS OF BONE TURNOVER

The purpose of this study was to examine the effect of intranasal salm on calcitonin (sCT) administration (200 IE), given either in the morni ng (8:00) or evening (21:00), on the known circadian variation in bioc hemical markers of bone turnover. An open, placebo-controlled, randomi zed, crossover study, with three 24 h studies of blood samples drawn e very third hour and urine collected in 3 h aliquots was undertaken. Su bjects consisted of nine healthy postmenopausal women, aged 58 +/- 7 y ears. Urinary CrossLaps (a measure of bone resorption) was measured by ELISA and corrected for creatinine (Cr), Serum osteocalcin (sOC) was measured by radioimmunoassay (RIA). The first 24 h study was performed without intervention. Prior to this control study the participants we re randomized to either morning (8:00) or evening (21:00) sCT (200 LE) , sCT administrations were given 4-5 days prior to and during the seco nd study, After a washing-out period of 2 weeks the participants were given 200 IE of sCT at the reverse time of the day 5 days prior to and during the third study. At all timepoints, urinary CrossLaps/Cr exhib ited a significant (p < 0.001) circadian rhythm with its zenith in ear ly morning and nadir in late afternoon. Both morning and evening admin istration of sCT significantly decreased the urinary excretion of Cros sLaps/Cr approximately 3-6 h after administration with a subsequent re bound effect, sOC did not exhibit a significant circadian variation an d was not affected by the calcitonin. The 24 h mean urinary CrossLaps/ Cr and sOC remained unchanged. Both morning and evening sCT significan tly decreased the urinary excretion of CrossLaps/Cr 3-6 h after admini stration, with a rebound effect approximately 12 h later. However, the present study does not indicate that neither evening nor twice-daily administration is superior to morning administration. (C) 1997 by Else vier Science Inc.