Magnesium trisilicate

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  • Magnesium trisilicate relieves the symptoms of indigestion and heartburn.
  • The recommended dose is 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.
Type of medicineAntacid
Used forIndigestion
Available asMixture and tablets

Acid occurs naturally in your stomach. It is produced to help break down and digest the food you eat. Antacids like magnesium trisilicate neutralise acid made by your stomach. This is helpful in conditions such as acid reflux which causes indigestion and heartburn.

Magnesium trisilicate is available as a mixture. It is also available in combination with other antacids in tablet form. Liquid preparations are considered to be more effective than tablet preparations, although tablet preparations are more convenient to use. It can be bought without a prescription from pharmacies and other retail outlets.

To make sure this is the right treatment for you, speak with your doctor or pharmacist before you start taking magnesium trisilicate:

  • If you have any of the following symptoms: bleeding, difficulty swallowing, being sick frequently, or unexplained weight loss.
  • If you are pregnant. This is because, if you are expecting a baby, medicines should only be given on the advice of a doctor.
  • If you have liver or kidney problems.
  • If you have been told by a doctor that you have low levels of phosphate in your blood.
  • If you are on a low-sodium (salt) diet.
  • If you are taking or using any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
  • If you have ever had an allergic reaction to a medicine.
  • Before you start this treatment, read the manufacturer's printed information leaflet attached to the pack. The leaflet will give you more information about magnesium trisilicate.
  • The dose for an adult is 10-20 ml (two to four 5 ml spoonfuls) of mixture. 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. You can stir magnesium trisilicate into a small glass of water to dilute it before swallowing if you like.
  • If you have been given tablets, check the label for the directions on how to take them, but 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.
  • Do not take magnesium trisilicate at the same time as any other medicines. This is because it 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.
  • 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 acid reflux. Losing some weight and eating 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.

Occasionally, people who have taken this medicine have experienced mild diarrhoea, stomach cramps or wind. Other side-effects are unlikely, but if you do experience any other symptoms, speak with your doctor or pharmacist.

  • 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 used within a period of time (often 28 days) or discarded.

  • If you are having an operation or dental treatment, tell the person carrying out the treatment which medicines you are taking.
  • Never take more than the prescribed dose. 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.
  • This medicine is for you. Never give it to other people even if their condition appears to be the same as yours.
  • Never 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.

Further reading & references

  • British National Formulary; 63rd Edition (Mar 2012) British Medical Association and Royal Pharmaceutical Society of Great Britain, London
  • Manufacturer's PIL, Magnesium Trisilicate Mixture BP; Thornton & Ross Ltd, The electronic Medicines Compendium. Dated May 2012.

Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.

Original Author:
Helen Allen
Current Version:
Peer Reviewer:
Prof Cathy Jackson
Document ID:
3802 (v23)
Last Checked:
Next Review:
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