Omeprazole

Omeprazole is a medicine that belongs to a group called proton pump inhibitors (PPIs). It reduces the amount of acid your stomach produces. This helps to protect your stomach and food pipe (oesophagus) from acid damage. It is used for several different stomach and digestive problems: Gastro-oesophageal reflux disease (GORD) – when acid from your stomach regularly travels back up into your oesophagus, causing heartburn, acid regurgitation, discomfort and sometimes inflammation. Stomach ulcers (gastric ulcers) and upper intestine ulcers (duodenal ulcers). Helicobacter pylori infection – a bacterium that can cause ulcers. Omeprazole is usually prescribed alongside two antibiotics to clear the infection. Ulcers caused by NSAIDs – medicines like ibuprofen or naproxen that can damage your stomach lining. Omeprazole can both treat these ulcers and prevent them from forming if you need to keep taking NSAIDs. Zollinger-Ellison syndrome – a rare condition where a tumour causes your stomach to produce too much acid. Acid-related indigestion (dyspepsia) – for short-term relief of symptoms like burning pain in your upper tummy, feeling bloated or feeling sick. You can get omeprazole either as a prescription medicine or, for adults over 18, you can buy short courses from a pharmacy for the short-term treatment of reflux symptoms such as heartburn and acid regurgitation.

The cells in the lining of your stomach contain tiny pumps called proton pumps. These pumps are responsible for releasing acid into your stomach to help digest food. In people with acid-related problems, these pumps can be overactive, producing too much acid. Omeprazole works by blocking these pumps. It switches them off, so the amount of acid your stomach makes is dramatically reduced. Once your stomach contains less acid, the lining of your food pipe and stomach can heal, and your symptoms – heartburn, pain, a sour taste in your mouth – will settle down. A single daily dose provides around-the-clock acid suppression because the effect lasts until your body naturally makes new pumps to replace the blocked ones.

Omeprazole capsules are labelled as gastro-resistant or sometimes "enteric coated". This means the capsule has a special coating that stops the medicine from dissolving in the acid of your stomach. Instead, it passes through your stomach intact and only releases the medicine once it reaches your small intestine. If the coating were not there, the acid in your stomach would destroy the omeprazole before your body could absorb it, and the medicine would not work. This is why you must swallow omeprazole capsules whole. Do not chew them, crush them, or open the capsule and take the granules without a liquid, unless your doctor or pharmacist has specifically told you that your particular brand can be mixed with food or drink.

The most important rules are: take your capsules at the same time each day and take them before a meal. General advice: Take omeprazole once a day, usually in the morning. If you are prescribed it twice a day, take it once in the morning and once in the evening. Swallow the capsule whole with a glass of water on an empty stomach, ideally at least 30 to 60 minutes before a meal. Taking it before food means it can start working before your stomach begins producing acid in response to eating. You can take it with or without food, but taking it on an empty stomach gives the best results. If you have difficulty swallowing capsules, ask your pharmacist for advice. For some brands, you can open the capsule and mix the granules with a small amount of slightly acidic liquid – such as fruit juice or apple sauce – but you must swallow the mixture immediately without chewing the granules. Always check the leaflet that comes with your medicine first. What if I miss a dose? If you miss a dose, take it as soon as you remember, unless it is nearly time for your next dose. In that case, skip the missed dose and take your next dose at the usual time. Do not take a double dose to make up for a missed one – this will not make it work faster and could increase your risk of side effects.

The length of treatment depends on the condition you are treating. If you bought omeprazole from a pharmacy (for short-term heartburn and acid reflux): take it for up to 14 days. If your symptoms have not improved or have got worse after 14 days, you must see a doctor. Do not simply buy another course. If a doctor prescribed omeprazole for indigestion: a typical course lasts between 4 and 8 weeks. PPIs should be taken for as short a time as possible to avoid long-term side effects. If you need long-term treatment (for example, for a chronic condition like Barrett's oesophagus): your doctor will prescribe the lowest effective dose that controls your symptoms, and you will be reviewed regularly. Long-term use is sometimes necessary, but it comes with risks that your doctor will monitor. When to stop a short course – with any short course, stop as soon as you feel better. You do not need to finish a 14-day pack if your symptoms have cleared up after 7 days. But if your symptoms return as soon as you stop, see your doctor – you may have a condition that needs longer or stronger treatment.

When you stop omeprazole after using it for several weeks, your stomach may temporarily start producing more acid than usual – a rebound effect. This can cause your heartburn or indigestion symptoms to return, sometimes worse than before. These symptoms usually settle down after two to four weeks of stopping the PPI and can be managed with an antacid or alginate (such as Gaviscon). Your pharmacist or GP will be able to advise you. If you have been on long-term omeprazole, your doctor may help you step down your dose gradually – for example, by reducing the frequency from once a day to every other day, or by switching you to a lower strength. Do not stop suddenly without medical advice if you have been taking it for months or years.

Most people tolerate omeprazole very well, especially when used for short courses. However, like all medicines, side effects can occur. Common side effects (affect between 1 in 10 and 1 in 100 people): Headache Stomach pain, feeling sick (nausea) or being sick (vomiting) Diarrhoea or constipation Farting more than usual (flatulence) These effects are generally mild and often settle as your body gets used to the medicine. Less common side effects: dizziness, a dry mouth, skin rashes, or swelling of the ankles (fluid retention). If these bother you, speak to your doctor or pharmacist. Serious side effects (rare, but you need to be aware of them): Severe diarrhoea that does not go away – this can be a sign of a bacterial infection called Clostridioides difficile in your gut. Long-term use of PPIs can increase the risk of this type of infection. If you develop severe or persistent diarrhoea, especially with stomach cramps and fever, contact your doctor. Bone fractures – long-term, high-dose use (over 12 months) may increase the risk of fractures in your hip, wrist or spine. Low magnesium levels (hypomagnesaemia) – signs include unusual tiredness, dizziness, muscle cramps or an abnormal heartbeat. This is very rare and usually only happens with long-term use. Vitamin B12 deficiency – with prolonged use (over two years), PPIs can reduce the absorption of vitamin B12, leading to symptoms such as fatigue, breathlessness and nerve problems. Kidney inflammation (acute tubulointerstitial nephritis) – a very rare but serious side effect that causes fever, rash and reduced urine output. Severe skin reactions – extremely rare, but if you develop a widespread rash, blistering or peeling of the skin, stop taking omeprazole and seek urgent medical attention. Vision changes – in very rare cases, omeprazole can cause blurred vision or other visual disturbances. If you notice any change in your eyesight, stop taking it and speak to your doctor. When to stop and seek medical help: You develop a severe allergic reaction – swelling of your face, lips, tongue or throat, or difficulty breathing. You have persistent watery diarrhoea, especially with blood or mucus. You experience a widespread rash or blistering skin. You feel your symptoms getting significantly worse while taking the medicine. Omeprazole will not usually affect your ability to drive, cycle or use machinery. However, if you feel dizzy or have problems with your vision after taking it, wait until you no longer have these side effects before driving.

Do not take omeprazole if: You are allergic to omeprazole or to any of the other ingredients in the capsules. This includes a sensitivity to other proton pump inhibitors (such as lansoprazole, pantoprazole, rabeprazole or esomeprazole). You are taking a medicine called nelfinavir (used to treat HIV infection). You have ever had an allergic reaction to any medicine that reduces stomach acid. If you have liver disease, kidney problems, or osteoporosis (weakened bones), speak to your doctor or pharmacist before taking omeprazole – you may need a lower dose or extra monitoring.

Omeprazole can affect how other medicines work, and some medicines can affect how omeprazole works. Medicines that should NOT be taken with omeprazole: Nelfinavir (HIV treatment) – using them together can stop nelfinavir from working properly. Medicines that need caution or a dose adjustment: Clopidogrel (a blood-thinning medicine to prevent strokes and heart attacks). Omeprazole can reduce the effectiveness of clopidogrel. If you need a PPI while taking clopidogrel, your doctor may prefer to prescribe a different PPI (such as lansoprazole or pantoprazole). Warfarin (another blood thinner). Omeprazole can increase the blood-thinning effect of warfarin, raising the risk of bleeding. If you take warfarin, your INR (clotting time) may need to be checked more often when you start or stop omeprazole. Cilostazol (for leg pain when walking). Omeprazole can increase the level of cilostazol in your blood. Diazepam, phenytoin, or methotrexate (high-dose). Omeprazole can increase the level of these medicines in your bloodstream. St John's wort (a herbal remedy for depression) or rifampicin (an antibiotic). These medicines can reduce the effectiveness of omeprazole. Safe combinations: Antihistamines (such as cetirizine, loratadine, or fexofenadine for allergies) are generally safe to take with omeprazole. The BNF, NHS, MHRA and EMA have not identified any clinically significant interactions between omeprazole and standard antihistamines. Antacids (such as Gaviscon) can be taken at the same time as omeprazole, but it is best to take them at a different time of day – for example, two hours before or after your omeprazole dose. If you take any regular medicines, always check with your doctor or pharmacist before starting omeprazole.

Yes. Omeprazole can affect the results of certain tests, including some blood tests, checks for specific types of tumours, and a test to look inside your food pipe and stomach (a gastroscopy). If you are referred for any of these tests, you may need to stop taking omeprazole for a few days or weeks beforehand. Always check with the staff at the hospital or clinic where the test is being done. Omeprazole can also cause false-positive results in some urine screening tests for cannabis (THC). If you are having such a test, make sure the laboratory knows you are taking omeprazole.

Pregnancy Omeprazole is the PPI that is preferred for use in pregnancy because there is more information about its safety. There is no good evidence that omeprazole is linked to miscarriage, birth defects, stillbirth, preterm delivery, or low infant birth weight. Some studies have suggested a possible link between the use of acid-reducing medicines in pregnancy and allergy or asthma in children, but most studies show that the vast majority of exposed children did not have these conditions. More research is needed. If you are pregnant or planning to become pregnant, you can usually take omeprazole, but you should speak to your doctor or pharmacist first. Breastfeeding You can usually take omeprazole while breastfeeding. Only small amounts pass into breast milk, and no side effects have been reported in breastfed babies. However, it is still sensible to check with your doctor or pharmacist first.

All proton pump inhibitors work in the same way – they block the acid pumps in your stomach. However, there are small differences. Omeprazole is the most widely prescribed PPI in the UK and is considered a first-line choice for most acid-related conditions. It has been used clinically since the late 1980s and has an extensive safety record. Lansoprazole is also a first-line PPI and is very similar to omeprazole in effectiveness. It may be preferred in patients who have experienced side effects with omeprazole, or where the interaction between omeprazole and clopidogrel is a concern. Esomeprazole is a stronger version of omeprazole and is usually reserved for patients who have not responded adequately to omeprazole or lansoprazole, or for certain specific conditions like severe oesophagitis. If one PPI does not work well for you or causes side effects, your doctor can prescribe a different one. All are effective options.

Omeprazole treats the acid, but lifestyle changes can make a big difference and may help you keep your symptoms under control with a lower dose or for a shorter time. Raise the head of your bed by about 10–20 centimetres (using bricks or bed risers). This stops acid from flowing back up your oesophagus while you sleep. Avoid eating large meals. Eat smaller, more frequent meals instead. Avoid eating for two to three hours before lying down or going to bed. Avoid or reduce trigger foods and drinks. Common triggers include fatty or spicy foods, chocolate, caffeine, alcohol, carbonated drinks, citrus fruits and tomatoes. Lose excess weight. Being overweight puts pressure on your stomach and can push acid back up. Stop smoking. Smoking relaxes the muscle that keeps acid in your stomach and also weakens your oesophagus. Wear loose-fitting clothing. Tight belts or waistbands can put pressure on your stomach and trigger reflux. For occasional heartburn that is not frequent enough to need a PPI, antacids or alginates (such as Gaviscon) can be effective.

Store below 25°C (room temperature) in a dry place, away from direct sunlight and heat. Keep the bottle or blister pack in its outer carton to protect it from moisture. Keep out of the sight and reach of children. Do not use the capsules after the expiry date shown on the packaging. If you have any leftover capsules, do not throw them in household waste or pour them down the sink. Take them to your local pharmacy for safe disposal.