Introduction:
Magnesium is one of the macroelements required to maintain normal body homeostasis. During studies, a positive effect in the prevention of cardiovascular disease, postmenopausal osteoporosis and diabetes was found. Unfortunately a deficiency of this element in the daily diet was observed, so supplementation is recommended. The aim of the study was to determine the influence of the kind of magnesium compound on the availability of Mg²⁺ with a tablet with an unmodified release rate.

Materials and methods:
The following preparations were used: Biomagnezja 150, Citromag B6 and Biomagnezja Plus (FZNP "Biochefa"). Examination of the release rate of the active substance was performed in a paddle apparatus at T = 37°C ± 0.5°C for 120 min., with a mixer at 50 revolutions/min. and using 0.1 mol/dm3 HCl (pH = 1.2). For analysis of the magnesium release, Statistica software with pharmaceutical extensions: Dissolution Profiles was used.

Results:
Analysis of the tested products showed that the % of magnesium released increased in the following order: Biomagnezja Plus, Biomagnezja 150, Citromag B6 and was respectively 45%, 61% and 70 %. The release rate constant increased in the same order and it was respectively 0.0138 min^-1, 0.0146 min^-1, 0.018 min^-1.

Conclusions:
The factors affecting the release of magnesium in vitro are the solubility of the compound, the presence of an inorganic anion or an organic ligand and the stability of the compound. A higher solubility makes a higher percentage of release. The presence of an organic ligand (hydrogen citrate) determines a greater percentage of the released dose in comparison with the magnesium oxide thereof.