[Dissolution velocity of different calcium preparations used in the clinical field].

BACKGROUND

Prescription of calcium supplements is a frequent practice, considering that diet is insufficient to cover daily requirements of this mineral.

AIM

To study the dissolution velocity in an acid solution, of different commercial calcium supplements.

MATERIAL AND METHODS

Hydrochloric acid was added to distilled water in increasing amounts to obtain a final pH of 6.9, 3.0, 2.5, 2.0 and 1.5. Eighteen commercial calcium preparations were incubated in these solutions for 60 min and dissolution velocity was measured as the percentage of elemental calcium found in solution after this incubation period.

RESULTS

Calcium carbonate preparations had a pH dependent dissolution velocity, ranging from 0.67 +/- 0.8% at pH 6.9 to 77.15 +/- 17.5% at pH 1.5. Using the solution with pH 1.5, the dissolution velocity of different preparations varied widely from 56 to 100%. Calcium acetate, followed by calcium citrate and dicalcic phosphate were the salts in tablets with better dissolution velocities. Among powders and effervescent preparations, those containing calcium lactogluconate and citrate had the better dissolution velocities (95 to 115%), that were independent of the solution's pH. A studied preparation with integral bone had a very low dissolution velocity, not surpassing 33 mg of calcium per tablet.

CONCLUSIONS

The dissolution velocity of different calcium carbonate preparations varies greatly and, in conditions of achlorhydria, it is negligible. Calcium lactogluconate and citrate dissolution velocities are independent of the solution's pH.