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Magnesium trisilicate

Magnesium trisilicate relieves the pain and discomfort of indigestion and heartburn.

The recommended adult dose dose is 10-20 ml three times daily between meals, and at bedtime.

If you are taking other medicines, do not take magnesium trisilicate within two hours (before or after) of your other medicines.

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About magnesium trisilicate

Type of medicine

An antacid

Used for


Available as

Liquid mixture and tablets

Antacids are medicines which help to neutralise the acid content of your stomach. They are most commonly used to provide quick relief of symptoms for intermittent bouts of mild indigestion or heartburn. Acid occurs naturally in your stomach. It is produced to help break down and digest the food you eat. Antacids neutralise the acid in your stomach for a short period, so they are best taken when the symptoms occur.

Antacids containing magnesium trisilicate are available as liquid medicine and also in tablet form. Liquid mixtures are considered to be more effective than tablet preparations, although tablets are often more convenient to use. You can buy antacids which contain magnesium trisilicate, without a prescription from pharmacies and other retail outlets.

Before taking magnesium trisilicate

To make sure that this is the right treatment for you, ask a pharmacist or doctor for advice before you start taking magnesium trisilicate if:

  • You have any of the following symptoms: difficulty swallowing, loss of blood, weight loss, or if you are being sick (vomiting).

  • You are pregnant. This is because if you are expecting a baby, medicines should only be taken on the advice of a doctor.

  • You are taking any prescription medicines. This is because antacids can reduce the absorption of many medicines.

  • You have problems with the way your kidneys work, or problems with the way your liver works.

  • You have been told by a doctor that you have low levels of phosphate in your blood.

  • You have ever had an allergic reaction to an antacid medicine.

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How to take magnesium trisilicate

  • Before you start taking the antacid, read the manufacturer's printed information leaflet attached to the pack. It will give you more information about magnesium trisilicate.

  • The recommended dose for an adult is 10-20 ml (two to four 5 ml spoonfuls) of liquid medicine. The dose for a child aged 5 to 12 years is 5-10 ml (one or two 5 ml spoonfuls). It is usually sufficient to take this dose three times daily between each of your meals and at bedtime, although you can take a dose whenever it is needed up to once an hour. Remember to shake the bottle well before measuring out your dose.

  • If you are taking tablets, check the label for the directions on how to take them. As a guide, it is usual to chew 1-2 tablets when required.

  • Antacids are best taken to relieve your symptoms when they occur, or when you are expecting them to occur, such as after eating a large meal. Unless your doctor has told you otherwise, it is not usual to take them regularly every day.

Getting the most from your treatment

  • If your symptoms do not improve within a few days, you should talk to your doctor about this.

  • Some foods may make your symptoms worse. Foods and drinks that have been suspected of this include peppermint, tomatoes, chocolate, spicy foods, hot drinks, coffee and alcoholic drinks. If it seems that a food is aggravating your symptoms, try avoiding it for a while to see if your symptoms improve. Also, try avoiding eating large meals, as these can make your symptoms worse too.

  • If you are overweight, it puts extra pressure on your stomach and encourages the symptoms of heartburn. Losing some weight and following a healthy balanced diet may help you.

  • Smoking increases the amount of acid produced by the stomach and may make your symptoms worse. If you are a smoker, speak with your doctor or pharmacist about how to quit.

  • Do not take antacids at the same time as any other medicines. This is because they can interfere with the way your body absorbs other medicines and may stop them from working properly. Try to leave at least two hours both before and after a dose of magnesium trisilicate before you take any other medicines.

  • Many magnesium trisilicate preparations contain significant amounts of sodium. If you are on a low-sodium diet, please get advice from a pharmacist about which antacid preparations are suitable for you to take.

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Can magnesium trisilicate cause problems?

Occasionally, people who have taken this medicine have experienced digestive symptoms such as mild diarrhoea, stomach cramps and belching. Other side-effects are unlikely but if you do experience any other symptoms, speak with your doctor or pharmacist for further advice.

How to store magnesium trisilicate

  • Keep all medicines out of the reach and sight of children.

  • Store in a cool, dry place, away from direct heat and light.

  • Check the label on the bottle for an expiry date. Once a bottle of mixture has been opened, it may need to be either used within a period of time (often 28 days), or discarded.

Important information about all medicines

Important information about all medicines

If you suspect that you or someone else might have taken an overdose of this medicine, go to the accident and emergency department of your local hospital. Take the container with you, even if it is empty.

If you are having an operation or any dental treatment, tell the person carrying out the treatment which medicines you are taking.

Do not keep out-of-date or unwanted medicines. Take them to your local pharmacy which will dispose of them for you.

If you have any questions about this medicine ask your pharmacist.

Report side effects to a medicine or vaccine

If you experience side effects, you can report them online through the Yellow Card website.

Further reading and references

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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