Antacid and laxative tablets containing magnesium oxide particles as the active ingredient characterized by: (i) the magnesium oxide particles contained therein having an average secondary particle size, measured by the laser diffraction scattering method, of from 0.5 to 10 .mu.m; (ii) the conte nt of the magnesium oxide particles amounting to 88% by weight or more; (iii) being substantially free from blackish or tabletting spot; and (iv) having a disintegration time of 10 seconds or less. The above tablets are antacid and laxative tablets containing magnesium oxide particles and being suitable for oral administration which have a high content of the magnesium oxide particl es and a short disintegration time and are substantially free from any tabletti ng failure or blackish or tabletting spot.
