Zantac (Ranitidine)

How does it work?

Zantac tablets, effervescent tablets, syrup and injection all contain the active ingredient ranitidine, which is a type of medicine called an H2 receptor antagonist. (NB. Ranitidine is also available without a brand name, ie as the generic medicine.) Ranitidine acts in the stomach to decrease the production of stomach acid.

Ranitidine works by blocking histamine H2 receptors that are found on the cells in the stomach lining. A natural body chemical called histamine normally binds to these receptors, causing the cells to produce stomach acid. By blocking the H2 receptors, ranitidine prevents histamine from binding to them. This stops the cells from producing stomach acid.

Stomach acid is produced in the stomach as a normal part of the digestive process. Normally the linings of the stomach and duodenum (an area of the intestine directly after the stomach) are protected by a layer that resists acid attack. However, if this layer is damaged, or large amounts of stomach acid are formed, an ulcer can develop on the lining of the stomach or duodenum. This is called a peptic ulcer.

Acid produced in the stomach can also sometimes flow back into the food pipe (oesophagus). This is called gastro-oesophageal reflux, and can cause pain and a burning sensation known as heartburn. It can also irritate and damage the lining of the oesophagus, causing a condition called reflux oesophagitis.

By reducing the production of stomach acid, ranitidine can be used to treat all these and other conditions. It stops excess acid flowing back into the foodpipe and can be used to relieve heartburn symptoms associated with acid reflux. It also allows the oesophagus to heal in reflux oesophagitis.

By reducing the amount of acid in the stomach and duodenum ranitidine relieves the symptoms of indigestion. It also allows peptic ulcers to heal, and prevents them from recurring.

Ranitidine can also be used to prevent and treat peptic ulcers that can occur as a side effect of non-steroidal anti-inflammatory drugs (NSAIDs), such as diclofenac.

Ranitidine is used to depress stomach acid production in various other conditions. It is used in varying doses and for varying lengths of time depending on the condition being treated.

What is it used for?

In adults:

  • Treating peptic ulcers.
  • Preventing recurrent bleeding from peptic ulcers.
  • Treating and preventing peptic ulcers in people taking non-steroidal anti-inflammatory drugs (NSAIDs).
  • Preventing bleeding from stress ulceration in the gut in people who are critically ill, eg in intensive care.
  • Gastro-oesophageal reflux disease.
  • Excessive secretion of stomach acid due to a tumour or enlargement of the pancreas (Zollinger-Ellison syndrome).
  • Chronic indigestion related to meals or that disturbs sleep, but which is not related to any of the above conditions.
  • Preventing inhalation of acid from the stomach (acid aspiration) whilst under general anaesthetic.
  • Preventing inhalation of acid from the stomach (acid aspiration) in pregnant women during labour.

In children aged 3 to 18 years Zantac tablets and syrup are used for:

  • Short-term treatment of peptic ulcers.
  • Gastro-oesophageal reflux disease.

Zantac injection may be given from six months of age for these uses.

How do I take it?

  • Ranitidine tablets and syrup can be taken either with or without food.
  • The number of tablets or amount of syrup to take, how often and for how long will depend on the condition being treated. It is important to follow the instructions given by your doctor. These will also be printed on the dispensing label that your pharmacist has put on the packet of medicine.
  • If you forget to take a dose take it as soon as you remember. However, if it is almost time for your next dose just skip the missed dose and take your next dose as normal. Don't take a double dose to make up for a missed dose.
  • Ranitidine is given by injection (either into a vein or a muscle) when treatment by mouth is not possible.


  • Stomach cancer can have similar symptoms to stomach ulcers, and these symptoms can be relieved by ranitidine. For this reason, if it is suspected that you have a stomach ulcer, your doctor should exclude the possibility of stomach cancer before you start treatment with this medicine. This is particularly important if you are middle aged or older and have new or recently changed indigestion symptoms. Otherwise, this medicine could mask the symptoms of stomach cancer and therefore delay diagnosis of this condition.
  • A large study has recently suggested that elderly people and people with diabetes, chronic lung disease, or an underactive immune system (for example due to treatment such as chemotherapy or radiotherapy, or diseases such as HIV) may have a higher risk of developing pneumonia while they are taking H2 receptor antagonist medicines such as this one. Ask your doctor for more information. While you are taking this medicine you should tell your doctor if you develop a cough or chest infection.

Use with caution in

  • Elderly people.
  • People with decreased kidney function.
  • Zantac effervescent tablets contain aspartame. As a result they should be used with caution in people with an inherited disorder of protein metabolism called phenylketonuria. The effervescent tablets also contain sodium, and so should be used with caution in people whose intake of sodium should be restricted.
  • Zantac syrup contains ethanol (alcohol) and as a result may not be suitable for children, pregnant or breastfeeding women, or those suffering from alcoholism, liver disease, epilepsy, or brain injury or disease.

Not to be used in

  • People with a history of blood disorders called porphyrias.

This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.

If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

  • This medicine is not known to be harmful when used during pregnancy. When it is given to women who are in labour or having a caesarean section it does not have any adverse effects on the labour, delivery or subsequent progress of the baby. However, as with all medicines, it is not recommended for other uses during pregnancy unless considered essential by your doctor. Seek medical advice from your doctor.
  • This medicine passes into breast milk. The effect on a nursing infant is not known, although it does not appear to be harmful. The manufacturer recommends that this medicine should not be used during breastfeeding unless considered essential by your doctor. Seek medical advice from your doctor.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.

Rare (affect between 1 in 1000 and 1 in 10,000 people)

  • Allergic reaction.
  • Skin rash.
  • Alteration in results of liver function tests.

Very rare (affect fewer than 1 in 10,000 people)

  • Diarrhoea.
  • Headache.
  • Dizziness.
  • Blurred vision.
  • Slow heart rate (bradycardia).
  • Inflammation of the liver (hepatitis).
  • Inflammation of the pancreas (pancreatitis).
  • Inflammation of the kidney (acute interstitial nephritis).
  • Reversible impotence.
  • Breast swelling or production of breast milk.
  • Hair loss (alopecia).
  • Pain in the muscles or joints.
  • Confusion.
  • Depression.
  • False perceptions of things that are not really there (hallucinations).
  • Decrease in the normal number of blood cells in the blood.

The side effects listed above may not include all of the side effects reported by the medicine's manufacturer.

For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

It is important to tell your doctor or pharmacist what medicines you are already taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. Similarly, check with your doctor or pharmacist before taking any new medicines while taking this one, to make sure that the combination is safe.

As ranitidine lowers the acidity in the gut it may reduce the absorption of the following medicines, which could make them less effective:

  • atazanavir
  • cefpodoxime
  • dipyridamole
  • erlotinib
  • gefitinib
  • itraconazole
  • ketoconazole
  • lapatinib
  • pazopanib
  • posaconazole
  • rilpivirine
  • ulipristal.

Ranitidine may increase the absorption of raltegravir.

Ask your pharmacist for advice if you are taking any of these medicines.

Ranitidine may oppose the effect of histamine (used to treat leukaemia) and is not recommended for people having this treatment.

Other medicines containing the same active ingredient

Prescription-only products:

  • Ranitic.
  • Ranitil.

Ranitidine tablets, effervescent tablets, oral solution and injection are also available on prescription without a brand name, ie as the generic medicine.

Non-prescription products include:

  • Boots heartburn relief tablets.
  • Gavilast.
  • Gavilast-P.
  • Lloyds pharmacy indigestion relief tablets.
  • Ranzac 75.
  • Superdrug heartburn and indigestion relief tablets.
  • Zantac 75.
  • Zantac 75 relief.

Ranitidine tablets can also be bought without a brand name, ie as the generic medicine.