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Lansoprazole treats indigestion and heartburn.

It can also treat stomach ulcers and a rare illness called Zollinger-Ellison syndrome.

Lansoprazole comes as capsules and tablets that dissolve in water. It is available on prescription only.

Brand names include:

  • Lanzol
  • Razolager
  • Zomel
  • Zoton FasTab

How lansoprazole works

Lansoprazole is a 'proton pump inhibitor'. It temporarily stops proton pumps in your body from producing acid in your stomach.

Get emergency help

You might need medical help if you:

  • get serious side effects
  • have a serious allergic reaction (anaphylaxis)
  • take too much

Serious side effects

Urgent advice: Tell your GP straight away if you have:

  • joint pain and a rash on parts of your body exposed to the sun
  • stomach pain that's getting worse
  • skin that's red, blistering or peeling
  • had diarrhoea that doesn't seem to be getting better

Serious allergic reaction

A serious allergic reaction (anaphylaxis) after taking lansoprazole is rare.

Emergency action required: Call 999 or 112 or go to your nearest emergency department (ED) if you:

  • get a rash that's itchy, red, swollen or blistered
  • are wheezing
  • get tightness in your chest or throat
  • have trouble breathing or talking
  • have swelling in your mouth, face, lips, tongue or throat

If you take too much

Emergency action required: Go to your nearest ED or phone your GP if you take too much lansoprazole and:

  • have flushed skin
  • feel sweaty
  • have a fast heartbeat
  • feel sleepy
  • have blurred vision
  • feel confused or agitated

Check if you can take lansoprazole

Lansoprazole can be taken by most adults. Children should only take lansoprazole if prescribed by a doctor.

It may not be suitable if you:

  • have ever had an allergic reaction to other medicines
  • have liver problems
  • are lactose intolerant
  • are vegetarian, as capsules may contain gelatin


If you are pregnant, think you may be pregnant or trying for a baby, ask your GP or pharmacist for advice before taking lansoprazole.

Lansoprazole isn't recommended during pregnancy. There's no evidence it's safe while you are pregnant.

If you're pregnant it's better to treat your symptoms without taking a medicine like lansoprazole.

Your GP or midwife may suggest eating smaller meals and avoiding fatty and spicy food. They may also suggest raising the top end of your bed so that your chest and head are above your waist when sleeping.

Your GP may recommend a different medicine to help with indigestion or excess stomach acid if you are pregnant. Talk to your GP about the best option for you.


If you are breastfeeding, ask your GP or pharmacist for advice before taking lansoprazole.

Lansoprazole may get into breast milk but it's not known if it harms the baby.

Your GP might recommend a similar medicine called omeprazole if you are breastfeeding.

Contraception and fertility

Lansoprazole doesn't affect any type of regular contraception including the combined pill.

It may reduce the effectiveness of one type of emergency contraception called ellaOne (ulipristal).

There's no evidence to suggest that taking lansoprazole will reduce fertility in either men or women.

When you start taking lansoprazole

You should start to feel better within 2 to 3 days of taking lansoprazole.

It may take up to 4 weeks for lansoprazole to work properly. You may still have symptoms during this time.

The dose of your medicine depends on your condition. Your GP may increase or decrease your dose.

Depending on your illness, you may only take it for a few weeks or months. Some people need to take it for longer, even for many years.

How and when to take it

Always take lansoprazole exactly as your GP has told you.

It's usual to take lansoprazole once a day in the morning.

For severe illness, you can take it 2 times a day - once in the morning and the evening.

Lansoprazole works best if you take it 30 minutes before a meal or snack. Swallow tablets and capsules whole with water or juice.

If you have problems swallowing, open the capsules and mix the granules with water or juice. You can also sprinkle them onto soft food. Ask your GP or pharmacist for advice on how best to take lansoprazole if you're unsure.

Liquid lansoprazole can be made to order if you cannot swallow pills.

If you forget to take it

If you take lansoprazole once a day, take the missed dose as soon as you remember, unless it's less than 12 hours until your next dose. In that case skip the missed dose.

If you take it twice a day, take the missed dose as soon as you remember, unless it's less than 4 hours until your next dose. In that case skip the missed dose.

Do not take a double dose to make up for a forgotten dose.

Stopping treatment

Do not stop treatment early because your symptoms have got better.

Your condition may not have been fully healed. It may reoccur if you do not finish your course of treatment.

Side effects of lansoprazole

Most people who take lansoprazole do not have any side effects.

If you do have any, they are usually mild and go away when you stop taking it.

Talk to your GP or pharmacist if side effects get worse or do not go away after a few days.

Common side effects may include:

  • headaches
  • diarrhoea
  • stomach pain
  • constipation
  • wind
  • feeling sick or vomiting
  • itchy skin rashes
  • feeling dizzy or tired
  • sore mouth or throat
  • feet or ankle swelling
  • depression

See the patient information leaflet that comes with your medicine for a full list of side effects.

Non-urgent advice: Find your patient information leaflet

Your patient information leaflet is the leaflet that comes with your medicine. You can find a digital version of the leaflet online.

Report side effects

You can report any suspected side effects to the the Health Products Regulatory Authority (HPRA): report an issue -

Similar medicines

If lansoprazole does not work or or you have difficulty taking it, your GP may suggest you try another proton pump inhibitor.

Lansoprazole is only available on prescription but you can buy other medicines like it directly from pharmacies.

Long term use

Levels of magnesium in your blood may fall if you take lansoprazole longer than 3 months.

This can make you feel tired, confused, dizzy and cause muscle twitches and an irregular heartbeat.

Taking lansoprazole for more than 1 year can increase your chances of certain side effects, including:

If you get any of these symptoms, talk to your GP.

If you've taken lansoprazole for a long time speak to your GP before you stop.

Taking lansoprazole with other medications

Tell your GP or pharmacist that you are on lansoprazole before taking new medicines.

Check if you're already taking:

  • digoxin (a heart medicine)
  • anti-fungals such as itraconazole, ketoconazole or posaconazole
  • methotrexate (for psoriasis and rheumatoid arthritis)
  • HIV medicines
  • theophylline (used to treat asthma)
  • tacrolimus (a medicine used to reduce your immune system)
  • antacids (used to treat heartburn or acid regurgitation)
  • phenytoin (an anti-epilepsy medicine)
  • rifampicin (an antibiotic)
  • blood thinners such as clopidogrel or warfarin
  • fluvoxamine (an antidepressant)

Herbal remedies and supplements

St. John's Wort may stop lansoprazole working as well as it should.

Tell your pharmacist or GP if you're taking herbal remedies, vitamins or supplements.


It's safe to take painkillers such as paracetamol and ibuprofen at the same time as lansoprazole.

Other heartburn medicines

You can take lansoprazole with an antacid, for example Gaviscon.

Take it 2 hours before or after your dose of lansoprazole.

Food and drink

Avoid foods that make your indigestion worse, such as spicy and fatty foods.

You should also try to limit acidic foods, caffeinated drinks and alcohol.

If you have symptoms at night, try not to eat for at least 3 hours before you go to bed.

Fact check

This content was fact checked by a pharmacist, a GP, the National Medication Safety Programme (Safermeds) and the Health Products Regulatory Authority (HPRA).

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This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.

Page last reviewed: 24 September 2021
Next review due: 24 September 2024