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Rennie: Uses, Side Effects & Precautions

Dr Roger Henderson
Reviewed by Roger HendersonReviewed on 29.04.2024 | 3 minutes read

Rennie is a common antacid used to treat indigestion. It usually comes as tablets to be chewed or sucked but is also available as an oral suspension (a form of liquid). It comes in lots of different flavours such as peppermint, spearmint, and orange, and is available without a prescription. All Rennie products are suitable for adults and children aged twelve and above.

The oral suspension is also suitable for children aged six and above.

All Rennie products are safe to use during pregnancy and breastfeeding.

Doctor’s advice

How do they work?

Indigestion is often caused by your stomach producing too much acid, which can irritate the lining of your stomach. Symptoms can include feeling bloated and full, belching, trapped wind, flatulence, feeling sick, pain and discomfort in your upper abdomen, and heartburn. Symptoms usually occur after eating or drinking and can be more common at night (especially heartburn). Heartburn is the result of stomach acid travelling up your oesophagus (food pipe). This effect is known as acid reflux. The acid irritates the lining of your oesophagus, resulting in a burning feeling in your chest.

Rennie products contain antacids such as calcium carbonate, magnesium carbonate, and sodium bicarbonate that work by neutralising stomach acid. Some Rennie products also contain alginates like alginic acid or sodium alginate. These are known as raft-forming agents. They help relieve heartburn by forming a layer of foam at the top of your stomach, preventing acid reflux up the oesophagus. Some Rennie products also contain simethicone, which helps relieve the discomfort caused by trapped wind. It is an anti-foaming agent that disperses trapped air bubbles.

How do I take them?

You can take Rennie products to relieve indigestion or prevent it from occurring. To prevent indigestion, you should take the medication after meals and just before going to bed. How much you can take varies depending on the product. You should only take one Rennie product at a time. Also, it is best to avoid drinking alcohol because it can worsen your symptoms. Note, Rennie products are only recommended for short-term use.

You should speak to your doctor if you have ongoing symptoms of indigestion for more than two weeks.

Should anyone not take Rennie products?

As always, do not take the medication if you are allergic to any of the ingredients in it. If your doctor has recommended that you follow a low calcium or sodium diet, you should speak with your doctor or pharmacist before using any Rennie products. If you have diabetes, it is best to try a sugar-free Rennie product. 

Rennie products can interact with other medications like certain antibiotics (called tetracyclines and quinolones). If you take any prescription, over-the-counter, or herbal medicines, you should ask your doctor or pharmacist whether it is safe for you to take a Rennie product. They may recommend you take your usual medications at a different time to the Rennie product. 

Are there any side effects?

Generally, Rennie products are unlikely to cause side effects. However, occasionally some people may experience some side effects such as feeling sick, being sick, stomach upset, and diarrhoea. If any side effects become bothersome, you should speak with your doctor or pharmacist.

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Dr Roger Henderson
Reviewed by Roger Henderson
Reviewed on 29.04.2024
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