Omeprazole belongs to the proton pump inhibitor (PPI) class of medications. Doctors prescribe omeprazole in varying milligrams (mg) to reduce stomach acid to help treat a variety of digestive conditions.

People can also use over-the-counter (OTC) omeprazole to relieve heartburn or acid reflux.

Although most people tolerate omeprazole well, there are certain risks when people use it for a long period of time.

In this article, we review the uses, side effects, and drug interactions of omeprazole.

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A doctor may prescribe omeprazole for intestinal or stomach ulcers.
Image credit: Siufaiho, 2006

A PPI will reduce the acid in the stomach, which will help heal the stomach lining to help treat a range of conditions.

The Food and Drug Administration (FDA) have approved omeprazole capsules and granules for the following medical conditions:

  • intestinal ulcers in adults
  • stomach ulcers in adults
  • Helicobacter pylori infections, in combination with antibiotic therapy
  • gastroesophageal reflux disease (GERD) in people aged 1 and above
  • GERD-induced erosive esophagitis in people aged 1 and above
  • maintaining healing of erosive esophagitis in people aged 1 and above
  • Zollinger–Ellison syndrome

People can use OTC omeprazole tablets to treat frequent heartburn that occurs two or more times per week.

However, doctors do not recommend omeprazole tablets for immediate heartburn relief because it can take up to 4 days before it has its full effect.

Omeprazole is a PPI. Proton pumps are also called hydrogen-potassium pumps, and they are located along the inner lining of the stomach. These pumps are responsible for releasing acid into the stomach.

PPIs such as omeprazole will block the release of acid, thus decreasing the acidity inside the stomach.

Omeprazole takes around 1 hour to block the production of stomach acid, and its maximal effect occurs around 2 hours after taking the pill. The action of omeprazole can continue for about 3 days.

Omeprazole is available in three dosage types. The table below lists these dosage types, plus their strengths in milligrams (mg).

Dosage formStrength
Omeprazole delayed release capsules10 mg
20 mg
40 mg
Omeprazole granules for oral suspension2.5 mg
10 mg
Omeprazole tablets20 mg

Doctors must make an accurate diagnosis before prescribing omeprazole, as each diagnosis requires different treatments.

The following table lists the dosing instructions for each use of omeprazole.

UseDosing instructionsFrequency of use
intestinal ulcers in adults20 mg once daily4 weeks, but some people may require a total of 8 weeks
H. pylori infections, along with 2 antibiotics20 mg twice daily along with 2 antibiotics10 days
H. pylori infections, along with 1 antibiotic40 mg once daily along with 1 antibiotic14 days
stomach ulcers in adults40 mg once daily4–8 weeks
GERD in people aged 1 and above20 mg once daily4–8 weeks
maintain healing of erosive esophagitis in people aged 1 and above20 mg once dailystudies have not explored its use past 12 months
Zollinger–Ellison syndrome60 mg once dailysome people with this condition have used omeprazole continuously for more than 5 years

Doctors prescribe omeprazole to children ages 1–16 based on their weight. The following table lists the recommended dosages in mg for each use of omeprazole in children based on their weight in kilograms (kg).

UseWeight-based dosing instructionsFrequency of use
treating GERD in people aged 1 and above
  • 5–9 kg: 5 mg
  • 10–19 kg: 10 mg
  • 20 kg or greater: 20 mg
once daily up to 4 weeks
treating erosive esophagitis due to GERD
  • 3–4 kg: 2.5 mg
  • 5–9 kg: 5 mg
  • 10–19 kg: 10 mg
  • 20 kg or greater: 20 mg
once daily for up to 4–8 weeks, but treatment is limited to 6 weeks in babies aged 1 month to 1 year old
maintain healing of erosive esophagitis in people aged 1 and above
  • 5–9 kg: 5 mg
  • 10–19 kg: 10 mg
  • 20 kg or greater: 20 mg
once daily

Researchers have not conducted studies on the efficacy of omeprazole past 12 months.

Doctors suggest taking omeprazole 30–60 minutes before a meal. If the doctor recommends taking omeprazole twice daily, the person should take it before breakfast and before supper.

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Headaches may be a side effect of omeprazole.

The side effects of omeprazole include:

Side effects that children may report are similar to those that adults report, except that they tend to complain more about fever and breathing issues, such as pharyngitis and sinus infections.

Healthcare providers should follow up with people using omeprazole if their symptoms persist throughout treatment, or if their symptoms quickly return after stopping the medication.

Some doctors will detect kidney dysfunction in people taking omeprazole. A part of the kidney called the interstitium may become inflamed, causing a condition called acute interstitial nephritis to develop. People must stop taking omeprazole if they develop this.

Some researchers have linked PPIs, including omeprazole, to Clostridium difficile diarrhea. This condition is a serious bacterial infection that can lead to hospitalization and be fatal.

Some studies report that PPIs may increase the risk of bone fractures. Healthcare providers should therefore prescribe the lowest effective dosage and limit its use to the shortest possible duration.

People taking omeprazole for long periods of time may become deficient in some vitamins and minerals, including vitamin B-12 and magnesium.

Some drugs may interact with omeprazole. People should tell their doctor which medications they are already taking.

Omeprazole may interfere with the action of some antiretroviral drugs. However, researchers have not consistently reported this effect.

Doctors should closely monitor people taking antiretroviral drugs and omeprazole together to ensure that the combination is safe. However, people should not use rilpivirine and rilpivirine-containing antiretrovirals at the same time as taking omeprazole.

People taking warfarin to prevent blood clots should use omeprazole with caution because the combination can increase their risk of bleeding. They may need more frequent blood testing to make sure that the dosage of warfarin is appropriate.

Some doctors have reported higher methotrexate levels in people taking high dose methotrexate with omeprazole. These people must provide frequent blood samples so that their doctors can detect rising levels.

Also, some researchers have suggested that omeprazole interacts with clopidogrel. Taking a high dosage of omeprazole can reduce the levels of clopidogrel in the blood, putting people at risk of blood clots.

People taking phenytoin or digoxin and omeprazole together may be at risk of toxicity. Doctors will monitor blood samples of phenytoin or digoxin closely when both drugs are required.

Some drugs need exposure to an acidic environment before the intestine can absorb them. By reducing the acidity of the stomach contents, omeprazole may interfere with the following drugs:

  • mycophenolate mofetil
  • iron
  • certain anticancer medications
  • certain antifungal medications

Existing research does not demonstrate that omeprazole is harmful during pregnancy. Studies from Sweden and Denmark showed that the chance of birth defects in women using omeprazole was similar to the usual birth defect rate in the population.

Researchers have found limited evidence to suggest that omeprazole is present in breast milk. The effects of infant exposure to omeprazole are also unclear.

The cost of omeprazole depends on the strengths. The table below provides the prices of each form and strength of 30 days of omeprazole taken once daily.

Omeprazole generic 30 capsules10 mg
20 mg
40 mg
Omeprazole generic 30 tablets20 mg$23.39
Prilosec 30 tablets20 mg$25.17
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The class of PPI medications include dexlansoprazole, esomeprazole, and lansoprazole.

The PPI class of medications includes five other drugs:

  • dexlansoprazole (Dexilant)
  • esomeprazole (Nexium)
  • lansoprazole (Prevacid)
  • pantoprazole (Protonix)
  • rabeprazole (Aciphex)

Other acid suppressing medications include the histamine2 receptor blockers (H2 receptor blockers). These medications also reduce stomach acid but use a different pathway than PPIs.

H2 receptor blockers typically work more quickly than PPIs, but their effects only last for 4–10 hours.

Omeprazole is an effective medication to reduce acid levels in the stomach and treat a variety of stomach related conditions. People can also use OTC omeprazole to treat frequent heartburn.

People typically tolerate omeprazole well, but there are some risks when they use it for long periods of time. Doctors should follow up with people taking PPIs to make sure the drug is working and determine when the person can stop taking the drug.

If someone needs long term treatment, doctors need to routinely monitor their vitamin B-12 and magnesium levels and suggest supplements as needed.