Calcium load during administration of calcium carbonate or sevelamer in individuals with normal renal function.
BACKGROUND
Under steady-state conditions urinary calcium (Ca) excretion corresponds to the Ca load in healthy subjects. However, in chronic haemodialysis patients reliable data on Ca load are not available. In these patients Ca-containing phosphate binders are suspected to play a role in the progression of arteriosclerosis via increased but not quantified Ca load. The present study evaluated the effect of calcium carbonate (CC) and sevelamer hydrochloride (SEV), a calcium-free phosphate binder, on serum Ca and urinary Ca excretion in healthy individuals.


METHODS
Twelve healthy male individuals were included in a monocentre, randomized, single-blind, placebo-controlled, three-way crossover phase I study. Concurrently with their meals, participants received 4 x 2 tablets of SEV (800 mg), CC (500 mg) or placebo for 6 days with 1-week washout between the treatment periods. During the study, weekly blood samples were taken and 24-h urine was collected each day for measurement of calcium, magnesium, phosphorus, chloride and iPTH.


RESULTS
Mean daily urinary phosphorus excretion was significantly lower in subjects undergoing SEV treatment compared to those taking placebo (P < 0.001). Mean daily total urinary excretion of calcium was significantly higher in CC-treated participants compared to those receiving placebo (P < 0.001). Mean 24-h calcium excretion during the 6 treatment days was 6.60 +/- 2.62 mmol [265 +/- 105 mg] (CC) versus 5.15 +/- 2.16 mmol [206 +/- 87 mg] (SEV) versus 4.95 +/- 1.63 mmol [198 +/- 65 mg] (Placebo). Taking into account nutritional calcium intake estimated from dietary records fractional calcium absorption was 8.7% (CC), 13.3% (placebo) and 14.8% (sevelamer).


CONCLUSIONS
Intake of calcium carbonate compared to placebo in contrast to sevelamer in healthy individuals was associated with increased total urinary calcium excretion indicating an increased calcium load due to increased intestinal calcium absorption.
Heinrich
Tilman
T
Department of Internal Medicine VI, Clinical Pharmacology and Pharmacoepidemiology, University of Heidelberg, 69115 Heidelberg, Germany.
Heidt
Hartmut
H
Hafner
Verena
V
Schmidt-Gayk
Heinrich
H
Jenetzky
Ekkehart
E
Walter-Sack
Ingeborg
I
Mikus
Gerd
G
Bommer
Jürgen
J
D000328:Adult; D000863:Antacids / Q000494:pharmacology*; D002118:Calcium / Q000097:blood* / Q000652:urine*; D002119:Calcium Carbonate / Q000494:pharmacology*; D002614:Chelating Agents / Q000494:pharmacology*; D003404:Creatinine / Q000652:urine; D018592:Cross-Over Studies; D006801:Humans; D007408:Intestinal Absorption / Q000502:physiology; D007668:Kidney / Q000502:physiology*; D008274:Magnesium / Q000652:urine; D008297:Male; D011073:Polyamines / Q000494:pharmacology*; D000069603:Sevelamer; D016037:Single-Blind Method; D055815:Young Adult
D000863:Antacids; D002614:Chelating Agents; D011073:Polyamines; D000069603:Sevelamer; D003404:Creatinine; D002119:Calcium Carbonate; D008274:Magnesium; D002118:Calcium