DISSOLUTION VELOCITY OF COMMONLY USED CAL CIUM SUPPLEMENTS

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 solut ion, 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 commerci al calcium preparations were incubated in these solutions for 60 min a nd dissolution velocity was measured as the percentage of elemental ca lcium found in solution after this incubation period. Results: Calcium carbonate preparations had a pH dependent dissolution velocity, rangi ng from 0.67 +/- 0.8% at pH 6.9 to 77.15% at pH 1.5. Using the solutio n with pH 1.5, the dissolution velocity of different preparations vari ed widely from 56 to 100%. Calcium acetate, followed by calcium citrat e and dicalcic phosphate were the salts in tablets with better dissolu tion velocities. Among powders and effervescent preparations, those co ntaining 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 ve locity, not surpassing 33 mg of calcium per tablet. Conclusions: The d issolution 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.