Antacids for ulcers
The antacids used for the treatment of ulcer disease or reflux disease are weak bases that neutralize gastric acid. Their capacity to neutralize acid in the lumen of the stomach results in a reduction in acid load delivered to the duodenum or oesophagus (in reflux). It also inhibits pepsin activity: at a pH higher than 4, the activity of pepsin decreases markedly.
Antacids without systemic effects are preferred. Non-systemic antacids contain a cation (usually magnesium or aluminium) that is poorly absorbed in the small bowel.
Antacids are effective in reducing symptoms because of their rapid onset of action. However, the neutralizing effect is of short duration and therefore multiple dosages are required per day.
Antacids containing aluminium (algeldrate) and/or calcium (calciumcarbonate) tend to have constipating properties, whereas those with magnesium (magnesiumoxide) tend to cause diarrhoea. For this reason, the most commonly used products contain both aluminium and magnesium. Due to absorption of sodium-containing antacids, these drugs should be used with caution in patients with heart failure.
Extra info: Antacids containing magnesium act locally in the stomach and are hardly absorbed. By their acid-neutralizing effect they raise the pH and thus inhibit pepsinogen activation and gastrin levels. Magnesium is not absorbed and hence draws water into the GI lumen and increases intestinal motility, which can cause diarrhoea.
What is the most common adverse effect of aluminium-containing antacids?
Extra info: Close Antacids containing aluminium are known to cause constipation (in contrast to the diarrhea promoting magnesium containing antacids).