Omeprazole
Also sold as: Losec, Risek
Usual adult dose
Usual adult dose: 20 mg once a day before breakfast for 4 to 8 weeks; some conditions need 40 mg a day. Swallow the capsule whole. For H. pylori it is combined with antibiotics as prescribed.
Your doctor may give you a different dose. Children's doses depend on weight.
Side effects
Common
- headache
- stomach pain
- nausea
- diarrhoea or constipation
- wind
Serious — get help
Stop taking it and see a doctor straight away if you notice:
- severe or watery diarrhoea that does not stop
- low magnesium with long use (muscle cramps
- irregular heartbeat)
- bone fractures with long use
- severe skin reaction
Do not take it, or take care, if
- Warning signs such as weight loss, trouble swallowing, vomiting blood or black stools — see a doctor before taking it
- Liver disease (use with caution)
- Long-term use only if your doctor advises
Interactions
Medicines that can react with this one.
Serious1 medicineDo not take these together unless your doctor says so.
- Clopidogrel
Omeprazole reduces the activation of clopidogrel and may weaken its protection against heart attack and stroke.
Moderate4 medicinesTake together only with care. Ask your doctor or pharmacist.
- Itraconazole
Reduced stomach acid lowers absorption of itraconazole capsules.
- Ketoconazole
Stomach acid reducers lower absorption of ketoconazole tablets.
- Methotrexate
Can raise methotrexate levels, especially with high doses.
- Warfarin
Omeprazole may increase the effect of warfarin; INR should be checked.
Minor3 medicinesUsually not a problem, but tell your doctor.
- Cefuroxime
Medicines that reduce stomach acid can lower absorption of cefuroxime tablets.
- Cyanocobalamin
Long-term use of omeprazole can reduce vitamin B12 absorption from food.
- Levothyroxine
Long-term omeprazole may reduce levothyroxine absorption; thyroid tests may need checking.