Esomeprazole: what it treats and what to know

Esomeprazole targets the acid pumps in the stomach wall and switches them off, so less acid reaches the stomach and the food pipe. The NHS describes it as a medicine for indigestion and heartburn, acid reflux and GORD, and for preventing and treating stomach ulcers. It is sometimes used for Zollinger-Ellison syndrome, a rare condition where a tumour of the pancreas or gut overproduces acid.

The class it belongs to, the proton pump inhibitors, also includes omeprazole, lansoprazole and pantoprazole. Esomeprazole is closely related to omeprazole, which is why the two share many cautions.

Esomeprazole comes as capsules, tablets and granules. Tablets and capsules are available in 20 mg and 40 mg strengths, and granules in 10 mg sachets. The NHS gives typical daily amounts of 20 mg for heartburn and ulcers, 20 mg to 40 mg for reflux disease and a much higher starting amount for Zollinger-Ellison syndrome. Your prescriber will decide what applies to you.

It is usually taken once a day, first thing in the morning, with or without food, though some people are told to take it twice a day. Swallow tablets and capsules whole with still water. If that is difficult, a capsule can be opened into water or a tablet dissolved in water. Granules are stirred into water and should not be chewed.

• Some people use it in a symptom-led way once things have settled, as directed by their prescriber.

• For a once-a-day dose, take a missed tablet if fewer than 12 hours remain before the next; for twice daily, the figure is 4 hours.

• One or two extra doses are unlikely to cause problems, but call NHS 111 if you have taken more than prescribed and feel unwell.

Most adults can take esomeprazole, and children only on a doctor's prescription. It is unsuitable if you have had an allergic reaction to it or to other medicines, or if you have liver problems. It is also on the list of medicines to discuss if you have an endoscopy booked, since it can disguise what the camera would otherwise show.

If you are buying the over-the-counter strength, see a doctor before using it when you have unplanned weight loss, repeated vomiting, vomit that resembles dark coffee grounds, tar-like stools, unusual weakness or pallor, chest or stomach pain, severe or persistent diarrhoea, or difficulty swallowing.

The commoner effects, seen in more than 1 in 100 people, are headache, nausea, vomiting, diarrhoea, constipation, stomach pain and wind. Each has simple self-care: resting and drinking fluids for headaches, sipping water if you are being sick, eating smaller meals and avoiding beans, pulses and onions for wind.

Rarer reactions affect fewer than 1 in 1,000 people. Seek advice from a doctor or NHS 111 for yellowing skin or eyes with dark urine and tiredness, for joint pain with a red rash on sun-exposed skin, or for severe and persistent diarrhoea. Swelling of the lips, mouth, throat or tongue, breathing difficulty, or fainting need a 999 call.

Longer-term use matters too. After three months blood magnesium may drop, causing tiredness, dizziness, muscle twitches or an irregular heartbeat. Beyond a year there is a higher chance of fractures, gut infections and vitamin B12 deficiency, and the medicine may mask stomach cancer symptoms.

With little information on esomeprazole in pregnancy, the NHS does not recommend it and says doctors may suggest omeprazole instead. During breastfeeding it may be possible to take it after talking to your doctor, as the amount in milk is probably too small to be harmful. There is no evidence that it reduces fertility in men or women.

Medicines named by the NHS as needing care include digoxin, cilostazol, clopidogrel, warfarin, the antifungals itraconazole, ketoconazole, posaconazole and voriconazole, methotrexate, HIV medicines, phenytoin, rifampicin, citalopram, diazepam and imipramine. St John's wort should not be taken with it. Because the list is not exhaustive, show your pharmacist everything you take.

Esomeprazole can usually be stopped without cutting down gradually, but after a long course the NHS advises talking to your doctor first, because rebound acid symptoms can occur.

It does not interfere with alcohol in the body, though alcohol drives more acid production and can worsen symptoms. It occasionally causes dizziness, drowsiness or blurred vision, so avoid driving if you are affected. Food can be eaten as usual, but rich, spicy, fatty and acidic dishes and caffeine are best limited.

People using it for over a year have regular health checks. Studies hint at a possible slight rise in stomach cancer risk after three years of use, but cause and effect are unproven.

Prescribed esomeprazole and the lowest-strength over-the-counter packs are both on the UK market. Over-the-counter products are intended for short-term heartburn in adults and carry limits in the pack leaflet.

Alternatives include other PPIs such as omeprazole, which is often chosen in pregnancy, as well as alginates and antacids for occasional symptoms. Report suspected side effects to the Yellow Card scheme.