Omeprazole belongs to a class of medicines called proton-pump inhibitors (PPIs) and was first launched under the brand name Losec. It is used to treat stomach ulcers as well as to relieve heartburn and indigestion.
Proton pumps are found on cells that line the stomach and are used by these cells to produce stomach acid. Omeprazole works by inhibiting the action of the proton pumps and this reduces the production of stomach acid.
Acid is produced in the stomach as a normal part of the digestive process. However, sometimes this acid can flow back into the food pipe (oesophagus). This is called gastro-oesophageal reflux leading to pain and a burning sensation known as heartburn. Stomach acid can also irritate and damage the lining of the oesophagus, causing a condition called reflux oesophagitis.
Omeprazole reduces the production of stomach acid and therefore stops excess acid flowing back into the oesophagus thus relieving heartburn symptoms associated with acid reflux. By reducing the amount of acid in the stomach and duodenum omeprazole also allows peptic ulcers to heal and prevents them from recurring. It also relieves the symptoms of indigestion caused by excess stomach acid.
Another common use for omeprazole is in the prevention and treatment of peptic ulcers that can occur as a side effect of non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, naproxen and diclofenac. NSAIDs relieve pain and inflammation by reducing the production of substances called prostaglandins, which help to protect the stomach lining from the gastric acid. This leads to irritation and damage to the stomach wall. Omeprazole is used to treat peptic ulcers that occur due to this irritation. It also relieves side effects such as indigestion that can be associated with taking these medicines. Omeprazole is commonly prescribed in combination with NSAIDs to help prevent peptic ulcers from developing.
Omeprazole is also given, together with antibiotics, to help eradicate a bacterium called Helicobacter pylori (H. pylori) from the stomach, which can contribute to the formation of peptic ulcers. Omeprazole helps create an environment in the gut in which the antibiotics can be more effective at killing the bacteria.
The number of tablets or capsules to take, how often and for how long will depend on the condition being treated, see below for further information.
The omeprazole capsules or tablets should be swallowed whole. They must not be chewed, broken or crushed, as this would destroy the special coat, allowing the omeprazole to be broken down in the stomach and making it ineffective.
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.
The recommended doses of omeprazole for adults are given below:
- For reflux such as heartburn and acid regurgitation, 20 mg once a day for 4-8 weeks. (If there is no improvement after 8 weeks you should consult a doctor). Once the gullet is healed you can take 10mg a day as prevention.
- For ulcers in the upper part of the intestine (duodenal ulcer), 20 mg once a day for 2-4 weeks. If the ulcer has not fully healed after 4 weeks, the dose can be increased to 40 mg once a day for a further 4 weeks.
- For ulcers in the stomach (gastric ulcer), 20 mg once a day for 4 weeks. If the ulcer has not healed take the same dose for a further 4 weeks. If there are still symptoms then the dose can be increased to 40 mg once a day for another 8 weeks.
- To prevent duodenal and stomach ulcers from coming back the recommended dose is 10 mg or 20 mg once a day. This may be increased to 40 mg once a day if necessary.
- For duodenal and stomach ulcers caused by NSAIDs (Non-Steroidal Anti-Inflammatory Drugs), 20 mg once a day for 4–8 weeks.
- To prevent duodenal and stomach ulcers if you are taking NSAIDs, 20 mg once a day.
- For ulcers caused by Helicobacter pylori infection and to stop them coming back, 20 mg twice a day for one week. (You should also be taking antibiotics at the same time, please consult a doctor for advice).
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 omeprazole. Just because a side effect is stated here does not mean that all people using this medicine will experience that or any side effect.
Common (affect between 1 in 10 and 1 in 100 people):
- Disturbances of the gut such as diarrhoea, constipation, nausea, vomiting, abdominal pain or wind (flatulence).
Uncommon (affect between 1 in 100 and 1 in 1,000 people):
- Dizziness or spinning sensation,
- Difficulty sleeping (insomnia),
- Pins and needles sensations (paraesthesia),
- Increased liver enzymes,
- Skin reactions such as rash, hives, itching or dermatitis,
- Feeling generally unwell (malaise),
- Swelling of the legs and ankles due to excess fluid retention (peripheral oedema),
- Fracture of the hip, wrist or spine in people with osteoporosis (see cautions).
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 omeprazole, please read the information provided with the medicine or consult a doctor or pharmacist.
Stomach cancer can have similar symptoms to stomach ulcers, and these symptoms can be relieved by omeprazole. 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. Otherwise, omeprazole could mask the symptoms of stomach cancer and therefore delay diagnosis of this condition. This is particularly important if you are middle aged or older and have new or recently changed symptoms.
Omeprazole is not recommended for people taking the antiplatelet medicine clopidogrel. This is because recent evidence has shown that omeprazole can make the clopidogrel less effective at preventing heart attacks and strokes. If you are currently taking this medicine in combination with clopidogrel, you should consult your doctor to discuss this. This medicine should only be used in combination with clopidogrel if your doctor feels it is essential.
Omeprazole should be used with caution in:
- Decreased liver function.
- People with osteoporosis or who are at risk of osteoporosis, for example people taking long-term corticosteroid medicines and women who have passed the menopause. (This medicine may increase the risk of breaking a bone - see the warning section above.)
- Vitamin B12 deficiency.
Omeprazole should NOT be used in:
- Allergy to any 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 omeprazole and inform your doctor or pharmacist immediately.
The patient information leaflet (PIL) is a leaflet containing specific information about medical conditions, doses and side effects. You can download a copy of the PIL here:
Patient Info Leaflet