Omeprazole dosage: the right dose for your condition

The BNF gives clear dose advice for omeprazole, based on what you are treating. In my own practice, I always pick the lowest dose that works, for the shortest time that is right.

Gastro-oesophageal reflux disease (GORD):

• Mild symptoms: 10 mg once daily (you can buy this over the counter)
• Moderate to severe symptoms: 20 mg once daily for 4 to 8 weeks
• Maintenance for confirmed oesophagitis (inflammation of the gullet): 10 to 20 mg once daily

Gastric and duodenal ulcers:

• Duodenal ulcer: 20 mg once daily for 4 weeks
• Gastric ulcer: 20 mg once daily for 8 weeks
• NSAID-related ulcer (caused by anti-inflammatory painkillers): 20 mg once daily for 4 to 8 weeks

Helicobacter pylori eradication:

• 20 mg twice daily as part of triple therapy for 7 days. You take it with two antibiotics, such as amoxicillin 1 g twice daily and clarithromycin 500 mg twice daily.

Zollinger-Ellison syndrome:

• Start at 60 mg once daily, then adjust to how you respond. Some people need up to 120 mg daily, split into more than one dose.

NSAID prophylaxis:

• 20 mg once daily if you are at risk of stomach problems from anti-inflammatory painkillers

Swallow omeprazole whole with water, ideally 30 minutes before breakfast. Do not chew or crush the capsule.

In older patients, I take extra care with the omeprazole dose. The BNF says you do not need to change the dose for age alone. But there are some important points to think about.

Older patients are more prone to the long-term side effects of PPIs. These include:

• Bone fracture risk: the MHRA has flagged a higher fracture risk with long-term PPI use in older patients
• Hypomagnesaemia (low magnesium): older adults are more likely to take other medicines, such as water tablets (diuretics), that lower magnesium further
• Drug interactions: many older people take several medicines at once. Omeprazole blocks an enzyme called CYP2C19, which can change how drugs like clopidogrel and phenytoin are broken down.
• B12 deficiency: older patients already have higher rates of low vitamin B12, and PPIs may make this worse

In my practice, I review PPI prescriptions in patients over 65 at their yearly medicine check. If the original reason no longer applies, I suggest cutting down step by step:

1. Reduce from 40 mg to 20 mg for two weeks
2. Then from 20 mg to 10 mg for two weeks
3. Then try stopping, using antacids when needed

NICE guidance backs this approach. It advises the lowest dose that works, with regular reviews, for everyone on long-term PPIs.

Omeprazole is licensed for children, and the BNF for Children gives doses based on weight. A specialist should always start this treatment, or be asked first.

Children aged 1 to 11 years:

• Body weight 10 to 20 kg: 10 mg once daily, raised to 20 mg if needed
• Body weight over 20 kg: 20 mg once daily, raised to 40 mg if needed

Children aged 12 to 17 years:

• GORD: 20 mg once daily for 4 weeks
• Ulcer healing: 20 mg once daily for 4 to 8 weeks

Newborns and babies under 1 year:

• 700 micrograms per kg once daily, raised if needed to 1.4 mg per kg (the most is 20 mg once daily in babies under 10 kg)

Some children cannot swallow capsules. For them, omeprazole comes as a dispersible (MUPS) tablet that you can mix with water or slightly acidic fruit juice.

You can also empty the capsule and mix the contents with yoghurt or fruit puree, then give it straight away without chewing.

I always remind parents to keep treatment as short as is clinically right. Regular follow-up with the prescribing team is essential.

Getting the timing and the method right makes a real difference to how well omeprazole works. I explain the following to my patients:

Timing:

• Take omeprazole 30 minutes before your first meal of the day
• Proton pump inhibitors work best before you eat, because they act on the acid pumps when these are switched on
• If you take it twice daily (for example, for H. pylori eradication), take the second dose 30 minutes before your evening meal

Method:

• Swallow the capsule whole with a glass of water
• Do not chew, crush or open the capsule (unless you use MUPS tablets)
• If you find swallowing hard, ask your pharmacist about the dispersible form

Missed doses:

• If you forget a dose, take it as soon as you remember. But skip it if it is nearly time for the next one.
• Do not take a double dose to make up for a missed one

Duration of treatment:

• Over-the-counter use for heartburn: up to 2 weeks
• Prescription for GORD: usually 4 to 8 weeks
• Ulcer healing: 4 to 8 weeks
• Long-term maintenance: only with regular medical review

You should not keep taking omeprazole forever without a clear medical reason.

The NHS guidance advises that you discuss whether you still need it at each prescription review.

The liver breaks down omeprazole using two enzymes, CYP2C19 and CYP3A4. This leads to several interactions that matter and may affect the dose.

Clopidogrel:

Omeprazole cuts how well clopidogrel works as a blood thinner. It blocks the enzyme CYP2C19, which clopidogrel needs to turn into its active form. The MHRA advises against taking them together.

If you need a PPI with clopidogrel, lansoprazole or pantoprazole are better choices.

Methotrexate:

PPIs can slow how the kidneys clear methotrexate, which can make it toxic. The BNF advises thinking about stopping the PPI for a while in patients on high-dose methotrexate.

Phenytoin and warfarin:

Omeprazole can raise the blood levels of both drugs. Check the INR more often when you start or stop omeprazole in patients on warfarin.

Antifungals:

Ketoconazole and itraconazole need stomach acid to be absorbed. Taking a PPI at the same time can greatly reduce how much the body takes up.

HIV protease inhibitors:

Omeprazole greatly lowers the levels of atazanavir and nelfinavir. You should usually not take them together.

I always check for interactions with the BNF interaction checker before I prescribe omeprazole.

This matters most in patients on many medicines, and especially in older patients, who often take several drugs at once.