i can understand your concern.
you see, Rantac MPS is a antacid and the role of antacids is to reduce the already formed acid in the stomach and to reduce the production of any new acid.
therefore, all antacids are to be ideally taken on an empty stomach. i.e., atlas 15 minutes before food.
but if you have taken it after meals, don't need to worry . it won't cause harm. may be the doctor in a hurry would have said wrong.
Dr. Anil kumar jain
Donot worry. The direction in the medicine sample is given by conventional rules. So, follow it. This is absolutely absurd that rantac mps la should be given after food. Role of magaldrate in rantac mps bottle is to convert gastric acid into two alkali named aluminium hydroxide and magnesium hydroxide,which leads to sustainable antacid effect. If you take this antacid after food,than the effect of this will be reduced because aluminium hydroxide will limit the action of digestive enzyme called pepsin on your food inside stomach. So, this leads to a bit of incomplete absorption of nutrients from diet. So,take antacid liquid about 10mins before meal. Donot panic if you have taken this medicine after meal. It will never cause you any massive harm or injury. Just change your routine from next time,as I said.