Co-magaldrox (Maalox®, Mucogel®), Co-simalcite (Altacite Plus®), Magnesium carbonate, Magnesium trisilicate, Magnesium trisilicate with magnesium carbonate and sodium bicarbonate, Simeticone with aluminium hydroxide and magnesium hydroxide (Maalox Plus®), Sodium alginate with calcium carbonate and sodium bicarbonate (Acidex®, Gaviscon®, Peptac®), Sodium alginate with potassium bicarbonate (Acidex Advance®, Gaviscon Advance®) 

  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 (including combination product).

Combination product: -

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 – see Histamine H2-receptor Antagonists (H2RA) monograph and Proton Pump Inhibitors (PPIs) monograph.

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)1, 2.

For patients on enteral feeds – see Interaction(s) with other Common Medicines used in the Perioperative Period. 

Patients Undergoing Anti-Reflux Surgery or Total Gastrectomy
Review continued need for antacids following surgery.

  Interaction(s) with Common Anaesthetic Agents

None1, 2, 3, 4, 5, 6.

  Interaction(s) 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 absorption1, 4.

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)1, 3, 6
  • Tetracycline antimicrobials (doxycycline)1, 3, 5, 6

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 interval1, 2, 3, 6.

Oral dexamethasone absorption is significantly reduced by magnesium trisilicate, with a reduction in bioavailability of 75%.  Large doses of some other 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 hours6.

Enteral feeds
Aluminium containing antacids have formed bezoars (relatively insoluble complexes) with the protein in enteral feeds which has resulted in blockage of enteral tubes1, 6.

  Further Information

Risk of aluminium toxicity
Absorption of aluminium from aluminium salts is enhanced by citrates which are found in many effervescent preparations e.g. soluble analgesia1, 2. Caution is needed in individuals with renal impairment as aluminium toxicity could occur1.



  1. Joint Formulary Committee. British National Formulary (online) London: BMJ Group and Pharmaceutical Press. [Accessed on 18th September 2021]
  2. Summary of Product Characteristics – Maalox Plus® (Simeticone with aluminium hydroxide and magnesium hydroxide) Suspension. SANOFI. Accessed via 18/09/2021 [date of revision of the text January 2021]

  3. Summary of Product Characteristics – Gaviscon Advance® (Sodium alginate with potassium bicarbonate) Aniseed Oral Suspnsion. Forum Health Products Limited. Accessed via 18/09/2021 [date of revision of the text March 2019

  4. Summary of Product Characteristics – Acidex® (Sodium alginate with calcium carbonate and sodium bicarbonate) Oral Suspension (PL 04917/0027). Pinewood Healthcare. Accessed via 18/09/2021 [date of revision of the text February 2018]

  5. Summary of Product Characteristics – MUCOGEL® (Co-magaldrox) SUSPENSION. Chemidex Pharma Ltd. Accessed via 18/09/2021 [date of revision of the text November 2017]

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