<prompt> Antacid combinations of magnesium and aluminium salts are superior to single component preparations because:They have rapid as well as sustained acid neutralizing actionThey are less likely to affect gastric emptyingThey are less likely to alter bowel movementAll of the above  <response>: Mg OH2 has a quick onset whereas Al OH3 acts for a long time. Mg salts cause osmotic diarrhea whereas Al salts cause constipation. Combination of these two agents minimizes the impact on bowel movements. 