Omeprazole to reduce stomach acid - Losec, Mepradec, Mezzopram

Omeprazole reduces the amount of acid produced in the stomach.

Some omeprazole capsules and tablets should be swallowed whole; others can be mixed with water or fruit juice to make swallowing easier - check the manufacturer's printed information leaflet from inside the pack for directions.

The most common side-effects are stomach upset and headache. These effects are generally mild and do not last long.

Type of medicine Proton pump inhibitor
Used for Healing or prevention of gastric or duodenal ulcers; gastro-oesophageal reflux disease; Helicobacter pylori infection; Zollinger-Ellison syndrome; acid-related dyspepsia; reduction of gastric acid during surgery
Also called Losec®; Mepradec®; Mezzopram®
Combination brand: Axorid® (omeprazole in combination with ketoprofen)
Available as Capsules, tablets, dispersible tablets, and injection

Acid is produced naturally in your stomach to help you digest food and to kill bacteria. This acid is irritant so your body produces a natural mucous barrier which protects the lining of your stomach. In some people, this barrier can break down allowing the acid to damage the stomach, causing inflammation, ulcers and other conditions. Other people can have a problem with the muscular band at the top of the stomach that keeps the stomach tightly closed. This may allow the acid to escape and irritate the oesophagus, causing heartburn. This is often referred to as 'acid reflux'.

Proton pump inhibitors such as omeprazole stop cells in the lining of the stomach from producing too much acid. This can help to prevent ulcers from forming, or assist the healing process where damage has already occurred. By decreasing the amount of acid, they can also help to reduce the symptoms of acid reflux disease, such as heartburn. Omeprazole is also given as one part of a treatment to get rid of Helicobacter pylori, a bacterium found in the stomach, which can cause ulcers.

Omeprazole is available on prescription. You can also buy short courses of omeprazole at a pharmacy for the treatment of reflux symptoms (such as heartburn) in adults.

Some medicines are not suitable for people with certain conditions, and sometimes a medicine may only be used if extra care is taken. For these reasons, before you start taking omeprazole it is important that your doctor or pharmacist knows:

  • If you are pregnant, trying for a baby or breast-feeding.
  • If you have any of the following symptoms: difficulty swallowing, loss of blood, weight loss, or if you are being sick.
  • If you have any problems with the way your liver works.
  • If you have ever had an allergic reaction to a medicine.
  • If you are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
  • Before you start this treatment, read the manufacturer's printed information leaflet from inside the pack. It will give you more information about omeprazole and will provide you with a full list of the side-effects which you may experience from taking it.
  • If you have bought omeprazole for reflux symptoms such as heartburn, take one or two (10 mg) tablets daily, preferably in a morning. You may need to take omeprazole for a day or so to control your symptoms. If your symptoms do not improve within this time, you should talk to your doctor about this. Swallow the tablet with a drink of water - do not chew or crush the tablet before you swallow. Do not take omeprazole for more than four weeks without speaking with a doctor.
  • If you have been prescribed omeprazole, take it exactly as your doctor tells you to. There are different strengths of tablets and capsules available so your doctor will tell you which is right for you. It is usually taken once a day. If you are taking it for either Helicobacter pylori eradication or for Zollinger-Ellison syndrome, it is likely you will be asked to take two doses a day. Your doctor will tell you which dose is right for you and the directions will also be on the label of the pack to remind you.
  • Omeprazole tablets and capsules contain small pellets which are specially coated to make sure that the medicine is absorbed correctly by your body. Do not chew the pellets. If you find capsules or tablets difficult to swallow, let your doctor know. Some omeprazole capsules and tablets can be mixed with water or fruit juice to make swallowing easier and your doctor can prescribe these for you.
  • Omeprazole can be taken before or after food, although taking it before food can be preferable.
  • If you forget to take a dose at your usual time, you can take it when you remember (unless it is nearly time for your next dose, in which case leave out the missed dose). Do not take two doses together to make up for a forgotten dose.
  • Try to keep your regular appointments with your doctor. This is so your progress can be checked.
  • A typical course of treatment lasts for one or two weeks if you are taking omeprazole for Helicobacter pylori eradication. It will last for one or two months if it is to allow an ulcer to heal. For all other reasons for taking omeprazole, your treatment will last for as long as is necessary to control your symptoms.
  • 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.
  • Recent studies suggest that there may be a slight increase in the risk of bone fractures when proton pump inhibitors like omeprazole are taken for longer than a year. If this affects you, your doctor will check that you are taking enough vitamin D and calcium to reduce this risk.
  • If you buy any medicines 'over-the-counter', always check with a pharmacist that they are safe to take alongside your other medicines.

Along with their useful effects, most medicines can cause unwanted side-effects although not everyone experiences them. The table below contains some of the most common ones associated with omeprazole. You will find a full list in the manufacturer's information leaflet supplied with your medicine. The unwanted effects often improve as your body adjusts to the new medicine, but speak with your doctor or pharmacist if any of the following continue or become troublesome.

Common omeprazole side-effects (these affect less than 1 in 10 people) What can I do if I experience this?
Stomach upset (such as feeling sick, stomach ache, or wind) Stick to simple meals - avoid rich or spicy foods
Diarrhoea Drink plenty of water. If it continues or becomes severe, let your doctor know
Constipation Try to eat a well-balanced diet and drink several glasses of water each day
Headache Ask your pharmacist to recommend a suitable painkiller

If you experience any other symptoms which you think may be due to the medicine, speak with your doctor or pharmacist for further advice.

  • Keep all medicines out of the reach and sight of children.
  • Store in a cool, dry place, away from direct heat and light.

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.

If you are having an operation or any dental treatment, tell the person carrying out the treatment which medicines you are taking.

Do not 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

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:
Dr Hannah Gronow
Document ID:
3249 (v27)
Last Checked:
20/06/2014
Next Review:
19/06/2017
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