<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>: Ref: KDT 6e p635 Mg OH2 has a quick onset whereas Al OH3 acts for a long time. Magnesium salts cause osmotic diarrhea whereas aluminium salts cause constipation. Combination of these two agents minimizes the impact on bowel movements. 