Antacids

Antacids are a group of medications that are used to lower acid levels in the stomach.

Antacids are often used to relieve symptoms of reflux disease (GORD), heartburn (dyspepsia) and peptic ulcer. Antacids help to relieve pain and discomfort but do not help to heal these conditions or prevent them from happening again.

There are lifestyle changes you can make to  that can help prevent symptoms from occurring. These include:

Antacids are usually used only when needed and are not often prescribed long-term. If you find that you need to take antacids regularly, every day for more than 1 or 2 weeks, talk to your doctor. 

Taking antacids may not be suitable if you have any of the following problems:

  • Bringing up (vomiting) blood. This may be fresh blood but it can look like ground coffee (called coffee-ground vomit).
  • Blood in your stools (faeces). This may be look like blood, or it may just make your stools look black.
  • Unintentional weight loss.
  • Difficulty swallowing, including food getting stuck in your throat (oesophagus).
  • Ongoing tummy (abdominal) pain or vomiting.

If you have any of the symptoms listed above you should contact your doctor urgently.

How do antacids work?

Antacids work by neutralising (lowering) the acid in your stomach that is used to help digestion. This can reduce the symptoms of heartburn and relieve pain.

Some antacids also coat the surface of the oesophagus (the tube between your mouth and your stomach) with a protective barrier against stomach acid, or form a gel on the stomach’s surface which helps stop acid going into the oesophagus.

Types and formulations of antacids

Antacids are available as chewable tablets or liquid. Liquids are more effective than tablets. They are sold as many brand names, but they have similar  ingredients, including:

  • aluminium hydroxide
  • magnesium carbonate
  • magnesium trisilicate

Sometimes extra ingredients are added to help treat other problems, such as:

  • simethicone to relieve flatulence
  • alginates to prevent acid flowing into your oesophagus.

Examples of antacids

  • Alu-tab®
  • Chewy Quick-Eze®
  • Mylanta P®
  • Mylanta Original®
  • Mylanta Double Strength®
  • Mylanta Rolltabs®
  • Quick-Eze®

How to take antacids

  • The dose of different antacids will be different – follow the dose instructions on the label or check with your doctor or pharmacist.
  • Antacids come as chewable tablets or liquid.
    • Chewable tablets: chew the tablets well; do not swallow them whole. 
    • Liquid: shake the liquid well before each dose so that the medicine is evenly mixed. 
  • Antacids are best taken when symptoms occur or are expected, usually after meals and just before going to bed (about 4 times a day). It's best to take antacids soon after eating because this is when you're most likely to get indigestion or heartburn.

Precautions – before taking antacids 

While most people can safely use antacids now and again, and they can be bought from supermarkets or over-the-counter from your pharmacy, they are not suitable for everyone. For example people with:

  • heart failure
  • problems with their kidneys or liver
  • high blood pressure.

If any of these apply to you, it’s important that you tell your doctor or pharmacist before taking antacids.

Some antacids are not suitable if you have an illness where you need to control how much salt (sodium) is in your diet, such as high blood pressure or some liver conditions. This is because antacids have high levels of sodium, which could make you unwell.

Precautions – when taking antacids

  • Other medicines: antacids can interfere with the absorption of other medicines, so you should not take these together. Generally, do not take other medicines within 2-4 hours of taking antacids.
  • Alcohol: this can irritate your stomach and make your symptoms worse.
  • Do not use antacids all the time: antacids are usually used every now and again and not usually prescribed regularly or long-term. If you find that you need to take antacids regularly, every day for more than 1 or 2 weeks, talk to your doctor.

Possible side effects

Like all medicines, antacids can cause side effects, although most people who take antacids do not have any. Common side effects are:

Side effects What should I do?
  • Diarrhoea (runny poo)
  • This can happen with magnesium-containing antacids 
  • Tell your doctor if troublesome
  • Constipation


  • This can happen with aluminium-containing antacids 
  • Tell your doctor if troublesome
  • Bloating, gas or flatulence (wind)
  • Stomach cramps
  • Feeling sick (nausea)
  • Tell your doctor if troublesome

Learn more

The following links have more information on antacids. Be aware that websites from other countries may have information that differs from New Zealand recommendations.

Antacids Patient Info, UK

References

  1. Antacids and simeticone New Zealand Formulary
  2. Managing dyspepsia and heartburn in general practice - an update BPAC, 2011
  3. Managing gastro-oesophageal reflux disease (GORD) in adults BPAC, 2014
Credits: Sandra Ponen, Pharmacist. Reviewed By: Angela Lambie, Pharmacist, Auckland Last reviewed: 12 Jan 2018