UK Clinical Pharmacy Association

Magnesium carbonate

Issues for surgery

Loss of symptomatic relief from dyspepsia and gastro-oesophageal reflux disease (GORD) if omitted.

Advice in the perioperative period

Elective and emergency surgery 

Omit dose(s) whilst fasting.

Perioperative considerations

For patients with increased risk factors for aspiration (e.g. pregnancy, obesity, non-fasted state in emergency surgery) consider administration of acid-suppressing medication (oral or intravenous) pre-operatively.

Post-operative advice

Restart post-operatively, when required.

Aluminium containing antacids should be used with caution in patients with renal impairment, particularly if also prescribed effervescent medications e.g. soluble paracetamol (see Further information).

For patients on enteral feeds – see Interactions with other common medicines used in the perioperative period.

Patients undergoing anti-reflux surgery or total gastrectomy

Review continued need for antacids following surgery.

Interactions with common anaesthetic agents


Interactions with other common medicines used in the perioperative period

Administration of antacids containing aluminium, calcium or magnesium might damage enteric coatings designed to prevent dissolution in the stomach and can impair absorption of other medications. If administering medication where a reduction in bioavailability could have a clinically significant effect on safety or efficacy (e.g. antimicrobials), administration of the medication should be separated from the antacid, to allow for appropriate absorption.


Common antimicrobials used in the perioperative period where a significant reduction in bioavailability has been shown or where there is a theoretical interaction include:

  • Quinolone antimicrobials (ciprofloxacin, levofloxacin)
  • Tetracycline antimicrobials (doxycycline)

Consult product literature for recommendations on separating doses to ensure absorption.


Administration of oral iron preparations should be separated from antacids to allow for appropriate absorption, consult product literature for recommended interval.


Large doses of some antacids can reduce the bioavailability of corticosteroids; however, it appears small doses do not interact. Given the uncertainty consider separating administration of oral corticosteroids and antacids by 2-3 hours.

Further information

None relevant.


Baxter K, Preston CL (eds), Stockley’s Drug Interactions (online) London: Pharmaceutical Press. [Accessed on 18th September 2021]

Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press. [Accessed on 18th September 2021]