BMA Concise Guide to Medicine & Drugs


Brand names Losec, Mepradec, Mezzopram, Zanprol

Used in the following combined preparation Axorid


Drug group Anti-ulcer drug

Overdose danger rating Low

Dependence rating Low

Prescription needed Yes (except some preparations for short-term relief of acid reflux symptoms)

Available as generic Yes


Omeprazole belongs to a group of drugs called proton pump inhibitors, which reduce stomach acid secretion by blocking the stomach’s acid-pumping mechanism itself. It is used to treat stomach and duodenal ulcers as well as reflux oesophagitis (in which stomach acid rises into the oesophagus) and Zollinger-Ellison syndrome. Treatment for an ulcer is usually given for four to eight weeks, although it may be given for much longer to prevent ulcers in high-risk patients, such as those taking long-term non-steroidal anti-inflammatory drugs (NSAIDs). Omeprazole may also be given with antibiotics to eradicate the Helicobacter pylori bacteria that can cause peptic ulcers. Reflux oesophagitis may be treated for four to 12 weeks. As well as being a prescription drug, omeprazole is available over-the-counter for the short-term relief of acid reflux symptoms such as heartburn in adults over 18 years old.

Omeprazole causes few serious side effects. As with other anti-ulcer drugs, it may mask signs of stomach cancer, so it is prescribed only when the possibility of this disease has been ruled out.


Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor. For over-the-counter preparations, follow the instructions and call your doctor if symptoms worsen.

How taken/used Tablets, capsules, injection, intravenous infusion.

Frequency and timing of doses 1–2 x daily; (2 x daily for doses above 80mg).

Adult dosage range 10–40mg daily and sometimes up to 120mg daily.

Onset of effect 2–5 hours.

Duration of action Up to 24 hours.

Diet advice None, although spicy foods and alcohol may exacerbate the underlying condition.

Storage Keep in original container at room temperature out of the reach of children. Omeprazole is very sensitive to moisture. It must not be transferred to another container and must be used within 3 months of opening.

Missed dose Take as soon as you remember. If your next dose is due within 8 hours, take a single dose now and skip the next.

Stopping the drug Do not stop the drug without consulting your doctor; symptoms may recur.

Exceeding the dose An occasional unintentional extra dose is unlikely to be a cause for concern. But if you notice any unusual symptoms, or if a large overdose has been taken, notify your doctor.


Adverse effects of omeprazole include headache, diarrhoea or constipation, nausea, and vomiting, which are usually mild and often diminish with continued use of the drug. Discuss with your doctor if these are severe or persistent. Rarely, a rash may develop; if so, you should stop taking the drug and consult your doctor. Long-term use of omeprazole may increase the risk of intestinal infections and, in women, hip fractures (see Prolonged use).


Warfarin The effects of warfarin may be increased by omeprazole.

Phenytoin The effects of phenytoin may be increased by omeprazole.

Clopidogrel The antiplatelet effect of clopidogrel is reduced by omeprazole.

Ciclosporin and tacrolimus Blood levels of these drugs are raised by omeprazole.

Atazanavir The effects of this drug are reduced by omeprazole.

Ketoconazole and itraconazole Blood levels of these drugs may be reduced by omeprazole.


Be sure to consult your doctor or pharmacist before taking this drug if:

· You have a long-term liver problem.

· You are taking other medicines.

Pregnancy No evidence of risk, but discuss with your doctor.

Breast-feeding The drug may pass into the breast milk. Safety in breast-feeding not established. Discuss with your doctor.

Infants and children Not usually recommended under 1 year. Reduced dose necessary in older children.

Over 60 No special problems.

Driving and hazardous work No special problems.

Alcohol Avoid. Alcohol irritates the stomach, which can lead to ulceration and acid reflux.


Long-term use of omeprazole may increase the risk of certain intestinal infections (such as Salmonella and Clostridium difficile infections) because of the loss of the natural protection against such infections provided by stomach acid. Prolonged use also increases the risk of hip fractures in postmenopausal women, and may reduce absorption of vitamin B12 and magnesium in the intestine.