For the purpose of quality evaluation of commercially available magnesium oxide (MgO) tablets, we studied their acid neutralization and dissolution behaviors. The dissolution test was carried out by the paddle method in 1st fluid (pH 1.2). The dissolution amount of MgO from tablets was determined by chelatometric titration. The medium pH was periodically measured. The neutralization reaction in 750 ml of 1st fluid was markedly different between two kinds of commercial tablets. The pH of medium including Magmit® tablet reached 8.9 and the dissolution rate of MgO was 81.1% after 20 min. Contrariwise, the final pH of medium including Maglax® tablet was 2.5 and the dissolution rate of MgO was 77.1% after 60 min. These results indicate that the dissolution rate of MgO from tablets should be >81.1% to obtain significant acid neutralization action.
