Comparison of calcium retention measured using a radionuclide method after administration of 1000 mg elemental...

A randomized, open, crossover, two-phase study was conducted to compare body retention of calcium measured using a radionuclide method after acute oral administration of 1 000 mg elemental calcium in two different galenic forms, in one or two doses. In the first phase of the study, which included 14 volunteers, the two treatments were one dissolve-in-the-mouth tablet of calcium carbonate in the morning and one in the evening (Orocal 500 mg) (treatment A1) and one effervescent tablet calcium carbonate (Cacit 1000) (treatment B). In the second phase in 8 volunteers, treatment A1 (Orocal 500 mg) was compared to two tablets of the same preparation in a single dose (Orocal 500 mg) (treatment A2). Each treatment contained a tracing dose of 47Ca. Body retention, expressed as the percentage of the total dose and measured seven and 14 days after each treatment, was significantly greater with Orocal 500 mg than with Cacit 1000 (24.21 +/- 3.38 versus 11.96 +/- 2.50 on day 7; 20.22 +/- 3.26 versus 9.67 +/- 2.56 on day 14; p < 0.001). Retention after administration of Orocal 500 mg was slightly better with two doses than with one dose (24.66 +/- 3.44 versus 21.32 +/- 7.63 on day 7; 20.19 +/- 3.28 versus 17.29 +/- 6.63 on day 14). Twenty-five per cent of the difference in calcium retention between treatments A1 (Orocal 500 mg) and B (Cacit 1000) was ascribable to the dosing schedule difference and 75% to the differences in galenic characteristics.