Brits who are taking a commonly prescribed medication have been issued a warning by the NHS. This drug, which is used to reduce the amount of acid produced by the stomach, can cause complications when combined with other medication.

Lansoprazole is typically prescribed for conditions such as indigestion, heartburn, acid reflux, and gastroesophageal-reflux-disease. It's also used in the prevention and treatment of stomach ulcers and a rare condition known as Zollinger-Ellison syndrome. According to the British Journal of Clinical Pharmacology, it ranks among the most frequently prescribed medications in England.

However, like all medications, Lansoprazole comes with certain warnings. The NHS website states: "Some medicines and Lansoprazole can affect each other and make it more likely that you will have side effects or stop one of the medicines working as well."

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Therefore, if you're taking any of the following medications, you should inform your doctor before starting lansoprazole treatment:

• Digoxin (a heart medicine)
• Antifungal medicines such as Itraconazole, Ketoconazole or Posaconazole
• Methotrexate (a medicine that treats psoriasis and rheumatoid arthritis)
• HIV medicines
• Phenytoin (an epilepsy medicine)
• Rifampicin (an antibiotic)
• Clopidogrel or Warfarin (medicines to prevent or treat blood clots)
• Fluvoxamine (an antidepressant)

The health body further stated: "These are not all the medicines that may not mix well with Lansoprazole. For a full list see the leaflet inside your medicines packet."

Some of the "common" side effects of Lansoprazole may happen in more than one in 100 people. You should talk to your doctor or pharmacist if these side effects bother you or do not go away:

• Headaches
• Feeling sick
• Diarrhoea or being sick (vomiting)
• Stomach pain
• Constipation
• Wind
• Itchy skin rashes
• Feeling dizzy or tired
• Dry mouth or throat

You should call a doctor or call 111 "straight away" if you have:

• Joint pain along with a red skin rash, especially in parts of your body exposed to the sun, such as your arms, cheeks, and nose (this may be less noticeable on brown or black skin) – these can be signs of a rare condition called subacute cutaneous lupus erythematosus. This can happen even if you've been taking Lansoprazole for a long time
• Stomach pain that seems to be getting worse – this can be a sign of an inflamed liver or pancreas
• Severe or persistent diarrhoea – this can be a sign of an inflamed bowel

You should also steer clear of taking Lansoprazole alongside a supplement known as St John's wort. The NHS further explained: "St John's wort may stop Lansoprazole working as well as it should.

"There's not enough information to say that other complementary medicines and herbal remedies are safe to take with Lansoprazole. They're not tested in the same way as pharmacy and prescription medicines. They're generally not tested for the effect they have on other medicines.

"Tell your doctor or pharmacist if you're taking any other medicines, including herbal medicines, vitamins or supplements."

Most adults and children can take Lansoprazole, but it is not suitable for some people. The NHS advises informing your doctor before taking Lansoprazole if you:

• Have ever had an allergic reaction to Lansoprazole or any other medicines
• Have liver problems
• Are pregnant, trying to get pregnant or breastfeeding
• Are due to have an endoscopy

For more information, visit the NHS website here.