[The quality evaluation of magnesium oxide tablet due to acid neutralization action]

For the purpose of quality evaluation of magnesium oxide (MgO) tablets, we considered the dissolution test method with changes in the pH of the dissolution medium as an indicator and studied the elution behavior of MgO from commercial MgO tablets. We also studied the effects of particle size on the elution rate of MgO from MgO tablets. A dissolution test was carried out using the rotating basket method in 100 ml of the first fluid (pH 1.2). The stirring speed was set at 200 rpm. The elution behaviors of MgO from two products were markedly different. The medium pH for the sample MM (Magmit) tablet after 15 min reached 9.5 but that for ML (Maglax) tablet was 2.7 even after 60 min. The apparent solubility of MgO in 100 ml of the first fluid were, respectively, 175 mg and 100 mg when medium pH as 9.5 and 1.5. The low dissolution of ML tablets is thought to be due to the large particle size (average particle size r = 226 microm) or due to the effects of additives on elution. These results suggest that neutralizing activity after ingestion of MgO tablets and subsequent laxative effects may, when conditions after ingestion of MM tablets and after ingestion of ML tablets are compared, produce differences between them. We found that the dissolution test method with pH as an indicator is useful in assessing the dissolution behavior of MgO preparations.