Omeprazole

Is omeprazole safe?

Yes. For a two-week course of heartburn treatment, omeprazole is about as safe as a medicine gets: no boxed warningBoxed warningThe strongest safety warning the US FDA puts on a medicine's label, printed inside a black border at the top.More in the glossary, no dependence, a very wide overdose marginOverdose marginHow far a normal dose is from a harmful one. A wide margin means an accidental extra dose is unlikely to cause serious harm.More in the glossary and more than 35 years of use. It is sold as Prilosec in the US, Losec in Britain and Europe, and as cheap generics everywhere. We score it 86.

The questions are about years of daily use, which is how many people end up taking it. Some long-term risks are real but small. Others that made headlines, such as dementia and kidney failure, look much weaker after a large randomised trial.

What years of use really does

Omeprazole is a proton pump inhibitor (PPI). It switches off most of the stomach's acid production, and acid does more than digest food. The US label lists these risks with long-term use:

• Gut infections. Less acid lets more bacteria survive, including C. difficile. PPIs are linked to a higher risk, especially in hospital patients.
• Low vitamin B12 after daily use for more than about 3 years, because B12 needs acid to be released from food.
• Low magnesium, usually after 3 months or more and often after a year. It can cause cramps, tremor and an irregular heartbeat, and is more likely with diuretics.
• Fractures of the hip, wrist and spine, mainly with high doses for a year or more in observational studies.
• Kidney inflammation (acute interstitial nephritis) and cutaneous lupus, which are rare.

The trial that tested the headlines

Most of the worrying long-term links came from observational studies, in which PPI users were older and sicker than non-users. The COMPASS trial, published in 2019, randomly assigned 17,598 people with heart or artery disease to pantoprazole, a close relative of omeprazole, or placebo for about 3 years. It found no difference in dementia, chronic kidney disease, fractures, pneumonia, stomach cancer or deaths. The one signal was enteric (gut) infections: 1.4% on pantoprazole and 1.0% on placebo.

That is reassuring, but it was one PPI, mostly in older people, over 3 years. The sensible approach remains the lowest dose that controls symptoms, with a regular review of whether you still need it.

Interactions to check

Medicine	Issue	Label advice
Clopidogrel (Plavix)	Omeprazole reduces its activation	Avoid together
Rilpivirine (HIV)	Absorption falls sharply	ContraindicatedContraindicationA situation in which a medicine should not be used, because the risk clearly outweighs any benefit, such as a known allergy to it.More in the glossary
St John's wort, rifampin	Omeprazole levels fall	Avoid
Methotrexate (high dose), tacrolimus	Levels can rise	Monitor or pause
Iron, some antifungals and HIV drugs	Need acid to be absorbed	Ask a pharmacist

Doses

Over the counterOver-the-counterA medicine you can buy without a prescription, in a pharmacy or shop, with directions on the pack for safe use without a doctor.More in the glossary in the US, Prilosec OTC is one 20 mg tablet a day before breakfast for 14 days, repeated no more often than every 4 months unless a doctor directs. On prescription, typical doses are 20 to 40 mg a day; people with Zollinger-Ellison syndrome have taken up to 120 mg three times a day. Omeprazole is often given for a week or two with amoxicillin and clarithromycin to clear H. pylori, and long-term to protect the stomach in people taking aspirin or ibuprofen.

Do you need a PPI at all?

For occasional heartburn after a big meal, an antacid such as Gaviscon or Tums, or an H2 blocker such as famotidine, may be enough and works within minutes to an hour. Omeprazole takes 1 to 4 days to reach its full effect, according to the Prilosec OTCOver-the-counterA medicine you can buy without a prescription, in a pharmacy or shop, with directions on the pack for safe use without a doctor.More in the glossary label, so it suits frequent heartburn rather than a single bad night. Weight loss, smaller evening meals, less alcohol and raising the head of the bed also help reflux, and they have no side effects.

Who should be careful

Heartburn that does not settle in two weeks, or comes with trouble swallowing, weight loss, vomiting or black stools, needs a doctor rather than more tablets, because omeprazole can mask stomach cancer. Ask your doctor or pharmacist before long-term use if you take clopidogrel, methotrexate, diuretics or HIV medicines, or if you have osteoporosis.

How we scored it

Overdose marginOverdose marginHow far a normal dose is from a harmful one. A wide margin means an accidental extra dose is unlikely to cause serious harm.More in the glossary (95), track record (95) and dependence (92) are strong. Interactions (70) and regulatory warnings (75) are lower because of the clopidogrel interaction and several FDA safety communications on long-term use.