Clopidogrel and omeprazole: why the NHS suggests another stomach medicine

The NHS describes clopidogrel as an antiplatelet medicine that prevents platelets, a type of blood cell, from sticking together and forming a dangerous blood clot. Risk is higher if you have had a heart attack, unstable angina, a stroke or mini-stroke, have peripheral arterial disease or atrial fibrillation, or have had an operation such as a coronary stent insertion.

Omeprazole is a proton pump inhibitor, or PPI. The NHS says it reduces the amount of acid in the stomach and is used to treat or prevent stomach ulcers, heartburn, gastro-oesophageal reflux disease and Helicobacter pylori infection along with antibiotics. Some types can be bought from pharmacies and shops.

The two can end up in the same person because a stomach-protecting medicine is sometimes added to other treatment. The NHS clopidogrel page says that if you have indigestion and need a medicine to protect your stomach, your doctor can prescribe another similar medicine.

In the BNF interaction list for omeprazole, the clopidogrel entry says that omeprazole is predicted to decrease the efficacy of clopidogrel, and that the manufacturer advises avoid. Severity is moderate and the evidence type is study. The clopidogrel list has a matching entry for esomeprazole, with the same advice.

The wording is about efficacy, meaning how well clopidogrel works, rather than about toxicity. It is a different type of interaction from those where a medicine builds up. The worry is that a person believes they are protected from clots when the protection may be weaker.

In the BNF clopidogrel list read for this guide there was no entry for lansoprazole, which is consistent with the NHS choosing it as an example of a similar medicine. That is an observation about the list, not a guarantee, so the prescriber chooses the specific alternative.

The NHS clopidogrel page says that omeprazole and esomeprazole may affect how well clopidogrel works. If you need a medicine for indigestion or to protect your stomach, your doctor can prescribe another similar medicine, such as lansoprazole, and you can take other indigestion remedies such as antacids at the same time as clopidogrel. A pharmacist can recommend a suitable indigestion remedy.

The NHS also says not to take aspirin for pain relief at 300mg or ibuprofen while taking clopidogrel unless a doctor says it is fine, since they increase the chance of bleeding, and that paracetamol is fine. It says not to drink grapefruit juice with clopidogrel, as it stops the medicine from working as well.

The NHS lists bleeding as the main side effect of clopidogrel: signs include nosebleeds, heavier periods, bleeding gums or bruising. It says to call 111 straight away for blood in your pee, blood in your poo or black tar-like poo, and to go to A&E for coughing up blood, vomiting blood or something like coffee grounds, a nosebleed that lasts more than 10 to 15 minutes, or a sudden bad headache with confusion, slurred speech or difficulty moving your arms or legs.

The sources read for this guide do not describe a symptom specific to reduced clopidogrel effect, which is why the practical step is review rather than symptom-watching. If you have chest pain, face drooping, arm weakness or speech trouble, call 999 whatever medicines you take.

If you take clopidogrel and buy omeprazole or esomeprazole over the counter, ask the pharmacist to check it first. If a prescriber has started a stomach-protecting medicine for you, check which one it is at your next medicine review. Do not stop clopidogrel or the stomach medicine yourself. This site has a separate guide to CYP2C19, clopidogrel and proton pump inhibitors for readers who want the mechanism.