Pharmacokinetics and pharmacodynamics of calcium-vitamin D(3) chewable tablets: a single-blind, multiple-dose study in postmenopausal women.

Objective: The objective of this study is to investigate the effect of a newly developed calcium carbonate-vitamin D₃ chewable tablet formulation (600 mg of calcium + 400 IU of vitamin D₃) on serum/urine calcium and serum parathyroid hormone (PTH) as measures of intestinal calcium absorption compared to a placebo.

Methods: This is a subject-blind, sequential study in 24 healthy postmenopausal women. Each subject received two placebo tablets once daily for 3 days (days -3 to -1) immediately followed by two calcium-vitamin D₃ tablets (test) during the subsequent 3 days (days 1-3). Serial blood sampling and 24-h urine collection took place on days -1 and 3. The subjects fasted until 6 h post-dosing. Total urinary calcium excretion (Ae(0-24 h)) and AUC(0-6 h) for serum calcium were the primary outcome variables and were compared between treatments using a paired sample t-test.

Results: Ae(0-24 h) increased by 42% (uncorrected, p = 0.0001) and 30% (creatinine-corrected, p = 0.0001), after intake, compared with the placebo; serum calcium exposure (AUC(0-6 h)) was also, statistically, significantly greater. PTH, in serum, decreased by 28% (AUC(0-6 h), p = 0.0001) and 14% (AUC(0-24 h), p = 0.0009) when compared with the placebo.

Conclusion: Daily intake of 1200 mg of calcium and 800 IU of vitamin D₃, with a new chewable tablet, resulted in increased intestinal calcium absorption compared to the results from the placebo as confirmed by direct and indirect pharmacokinetic/pharmacodynamic measures.