Pharmacokinetics of calcium absorption from two commercial calcium supplements

This study was conducted to compare pharmacokinetic indices of calcium abso rption after a single oral (500 mg calcium) load of Citracol (calcium citra te) and Os-Gal (calcium carbonate). In 18 postmenopausal normal women, veno us blood samples were obtained for the measurement of calcium before and ho urly for 6 hours after an oral ingestion of Citracal, Os-Cal, or placebo wi th a breakfast meal. The change in area under the curve (Delta AUC) in seru m calcium from preload was 2.5-fold greater for Citracal than Os-Gal, and t he peak-basal variation in serum calcium was 76% higher for Gitracal than O s-Gal. The increment in serum calcium from preload after Gitracal administr ation was significantly higher than that obtained after placebo load during most time periods and significantly higher than that of Os-Gal at 1, 4, an d 5 hours after load. In contrast, Delta AUC and peak basal variation of Os -Gal did not differ significantly from placebo, and increment in serum calc ium was significantly increased from placebo only at 6 hours. In conclusion , Gitracal is much more bioavailable than Os-Gal. (C) 1999 the American Col lege of Clinical Pharmacology.