Tagamet tablets and syrup contain the active ingredient cimetidine, which is a type of medicine called an H2 receptor antagonist. (NB. Cimetidine is also available without a brand name, ie as the generic medicine.) Cimetidine acts in the stomach to decrease the production of stomach acid.
Cimetidine works by blocking 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, cimetidine 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 cimetidine 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 cimetidine also allows peptic ulcers to heal, and prevents them from recurring. It also relieves the symptoms of indigestion caused by excess stomach acid.
Cimetidine can 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. In addition it can relieve side effects such as indigestion that can be associated with these medicines.
Cimetidine is also 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.
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.
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.
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.
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.
Cimetidine can increase the blood levels of various other medicines by slowing their breakdown by the liver. You should tell your doctor or pharmacist what medicines you are taking, including those bought without a prescription and herbal medicines, before you start treatment with this medicine. This is particularly important if you taking any of the medicines mentioned below, because your doctor may need to monitor your treatment or alter your medicine doses. Similarly, you should check with your doctor or pharmacist before taking any new medicines during treatment with this one, to ensure that the combination is safe.
Cimetidine increases the blood levels of the following medicines and may therefore increase the risk of their side effects:
Due to its effect on the acidity in the stomach, cimetidine may reduce the absorption of the following antifungal medicines from the stomach, which could make them less effective at treating infection:
If you are prescribed a course of one of these antifungals while taking regular cimetidine, it is recommended that you take each dose of the antifungal with an acidic drink such as cola, as this will help the antifungal to be absorbed.
Cimetidine may also reduce the absorption of the anti-HIV medicine atazanavir from the gut. The manufacturer of atazanavir recommends that it should be taken two hours before, or at least ten hours after taking cimetidine.
The anti-HIV medicine amprenavir may increase the blood level of cimetidine and may therefore increase the risk of its side effects.
Cimetidine tablets and oral solution are also available without a brand name, ie as the generic medicine.