Antacids

Introduction

Antacids (usually containing aluminium or magnesium compounds) can often relieve symptoms in dyspepsia.

  • They are best given when symptoms occur or expected, usually between meals and at bedtime.



Choices

Onset and duration
  • Liquid preparations have a faster onset of action.
  • Sodium and potassium salts are the most highly soluble, which enables them to have a quicker onset, but are shorter acting.
  • Magnesium and aluminium salts are less soluble, so these have a slower onset, but longer duration of action.
  • Calcium salts have the advantage of being quick acting and have a prolonged action.
  • It is therefore common for manufacturers to combine two or more antacid ingredients together to ensure a quick onset and prolonged action.
Precautions and side effects
  • Different from magnesium hydroxide and aluminium hydroxide, sodium bicarbonate may cause "belching" of carbon dioxide, which makes it less suitable in patients who have flatulence.
Neutralisation of Antacids
  • Magnesium salts tend to cause diarrhoea, and aluminium salts tend to cause constipation.
  • Preparations that are high in sodium should be avoided by anyone on a sodium-restricted diet (e.g. those with heart failure or kidney or liver problems).



Drug Interactions

A provisional registered pharmacist asked me quite an interesting question, it has been known that co-administration of antacids may affect absorption of other drugs and hence its efficacy, is it still advisable to give a combination of ranitidine and magnesium trisilicate mixture to a gastric patient.

Just for the background knowledge, all antacids potentially may increase or decrease the rate and/or extent of absorption of concomitantly oral drugs by changing GI transit time or by binding or by chelating the drug. It is best to separate taking antacids and other medications by at least 2 hours.

Few examples may include:
  • Bisphosphonates (e.g. alendronate, clodronate, risedronate)
  • Bisacodyl tablet
  • Deferasirox dispersible tablet
  • Deferiprone oral liquid
  • Dolutegravir - take antacids 6 h before or 2 h after
  • Eltrombopag olamine - take at least 2 h before or 4 h after antacids
  • Itraconazole capsule
  • Lanthanum
  • Ketoconazole tablet
  • Mycophenolate mofetil
  • Nilotinib
  • Quinolones (e.g. ciprofloxacin, levofloxacin, moxifloxacin, ofloxacin)
  • Tetracycline (e.g. doxycycline, minocycline, tetracycline)


Ranitidine and Magnesium Trisilicate Mixture

Well, is it fine for us to take ranitidine together with magnesium trisilicate mixture?

I did a google search as you would have expected, and find this 2001 journal article which concluded that there could be a synergy between low-dose ranitidine and antacid in decreasing gastric and oesophageal acidity and relieving meal-induced heartburn.



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