Omeprazole (Prilosec)
January 30, 201903,005

Omeprazole (Prilosec)

Omeprazole is a popular over-the-counter medication used to treat frequent heartburn. It is also available as a prescription medication used to treat more serious conditions, such as gastroesophageal reflux disease (GERD) and several other conditions where stomach acid is a problem. Even though omeprazole is a very popular and generally safe medication, it does have certain side effects, drug interactions and general precautions that need to be taken before using it.

What is Omeprazole?

Omeprazole is a Proton Pump Inhibitor (PPI). PPIs act on the cells of your stomach lining, causing them to make less stomach acid.1,3,12

One of the most commonly used PPIs is omeprazole. Omeprazole is available under the brand names of Prilosec (prescription) and Prilosec OTC (non-prescription).3,12 Prilosec is available as a delayed-release capsule or as sachets of delayed-release granules, which can be dissolved in water.3 Prilosec OTC is available as a delayed-release capsule or tablet.12

The reason that all the Prilosec products are “delayed-release” is to prevent stomach acid from breaking them down. They are therefore designed to make it through the stomach into the small intestine, where they can safely be absorbed.12

Omeprazole is also available in combination medications, such as Zegerid and Zegerid OTC, where it is combined with an antacid, sodium bicarbonate.12


Omeprazole prescription bottle with side effects info sheet.15


Omeprazole Uses

Since omeprazole is a PPI, it is useful for treating any condition where your stomach needs to make less acid in order for you to heal.1,12 If you have frequent heartburn (two or more times per week), without a more serious underlying condition, you may be able to use non-prescription omeprazole successfully.12 If you have a more serious condition, omeprazole will need to be prescribed by your doctor.3,12

Examples of more serious conditions that can be treated by prescription omeprazole include:

  • Duodenal ulcers (sores in the lining of your small intestine).3,12
  • Stomach ulcers (sores in the lining of your stomach).3,12
  • Helicobacter Pylori infection (a specific type of bacterial infection that can lead to stomach ulcers).5
  • Heart burn caused by GERD.1,3,12
  • Damage done to the lining of the esophagus caused by acid flowing back into it.3
  • Zollinger-Ellison syndrome (a rare condition where the stomach produces too much acid).3,9

Omeprazole Dosage

The doses of omeprazole vary depending on what the type of omeprazole you are using, the condition you have and how old you are.3

Adult Dosage

If you are older than sixteen years old, and wish to try out non-prescription omeprazole, these are the doses you will need:

  • The non-prescription delayed-release capsules or tablets should be taken once every morning, at least one hour before eating breakfast, for 14 days in a row.12
  • Another 14 days of treatment can be used every four months if you find that the heart burn returns (not more often though).12
  • If you then decide to go to your doctor, let them know if you have exceeded this maximum dose of non-prescription omeprazole before they prescribe you anything else to treat your heart burn.12

If you are experiencing GERD, stomach ulcers, duodenal ulcers or Ellison-Zollinger syndrome, you will need a prescription from your doctor for omeprazole.3

This is how long you may need to go on treatment for:

  • Eight weeks for duodenal and stomach ulcers.3
  • Ten to fourteen days together with antibiotics for pylori infection. Another fourteen to eighteen days may then be necessary after the antibiotics have been stopped. This is to prevent stomach ulcers.3,5
  • Four weeks for GERD symptoms.3
  • Eight weeks to allow healing of a damaged esophagus, known as erosive esophagus (EE). Your doctor may then decide to put you on another four weeks of treatment after that if the damage still has not healed enough.3
  • Long-term treatment for Ellison-Zollinger syndrome.3,9

It is not known whether it is safe to take omeprazole for longer than twelve months for the purpose of healing your esophagus if it is damaged.3,12 Your doctor will be able to advise you on what the best course of action is.

This is how much omeprazole you may need to take:

  • Once every day for GERD symptoms, stomach ulcers, duodenal ulcers or EE.12
  • Twice every day for pylori infections.12
  • Three times every day for conditions where the stomach makes too much acid, such as Ellison-Zollinger syndrome.12

Omeprazole should always be taken at least one hour before meals.3,12

Child Dosage

If you are younger than sixteen years old, or if you have a child who is, slightly lower doses of omeprazole may be needed compared to those needed by adults.3 This is how long you or your child may need to go on treatment for:

  • Four weeks for GERD symptoms.3
  • Eight weeks for healing of damage done to the esophagus by GERD.3

If you have an infant who is between one month and twelve months old, omeprazole can be used under the direction of your doctor. They may need to go on treatment for up to six weeks for GERD and acid-related damage done to the esophagus by GERD.3


Omeprazole Side Effects

If you do not take more than the recommended dose, Omeprazole is usually safe, but there are some common side effects that you may experience. These side effects vary from mild to severe depending on how much omeprazole you use, how long you use it for and how sensitive you are to it.1,3,12

More Common Side Effects

Some of the milder, more common side effects of omeprazole include:

  • Gas
  • Bloating
  • Constipation
  • Nausea
  • Vomiting
  • Headaches3,12

Let your doctor know if these symptoms become severe or are causing you discomfort.

Serious Side Effects

Some of the more serious side effects of omeprazole include:

  • Rashes, itching or hives on your skin.12
  • Swelling of your tongue, throat, lips, face, eyes, hands, ankles or feet.12
  • 12
  • Diarrhoea– Omeprazole can increase your risk of getting an infection in your intestines caused by the bacteria Clostridium difficile. Let your doctor know urgently if you begin to experience diarrhoea symptoms (loose stools, stomach cramps and fever).3
  • Bone fractures (long-term) – if you take omeprazole a few times a day for longer than twelve months, it is possible that your bones could weaken, putting you at risk of hip, spine or wrist fractures. It is best to take the least amount of omeprazole for the shortest amount of time you can. This will decrease your risk of getting bone fractures.3
  • Vitamin B12 deficiency– this vitamin needs acid in the stomach for it to be absorbed well. If omeprazole is taken for longer than three years, it is possible that you could develop a B12 deficiency.3
  • Low magnesium levels in the body– this can happen anytime from three months of being on omeprazole treatment, but is more likely if you have been on treatment for longer than a year.3 Symptoms of low magnesium levels include:
    • Muscle cramps.
    • Hand and feet spasms.
    • Seizures, jerking movements or shaking.
    • Spasms of the voice box.
    • Abnormal or very fast heartbeat.3

Let your doctor know immediately if you begin to experience any of these serious side effects. Get to your nearest emergency room if the symptoms become severe.


Warnings for Omeprazole Use

As you can see from the above side effects, it is very important to take omeprazole in a safe way. There are certain precautions that can be taken to ensure that omeprazole works properly and does not have any negative effects on you.3,12


General Warnings

The following are a few general recommendations you should follow when taking omeprazole:

  • It is very important to only use omeprazole if you have one of the conditions discussed above.12
  • If you have a condition that needs prescription omeprazole, do not take more than prescribed by your doctor.3
  • If you are taking non-prescription omeprazole for heart burn, make sure you do not take more than is recommended on the box.12
  • Do not give your omeprazole to anyone else, even if they seem to have similar symptoms to you. It could be harmful to them.3
  • Do not stop taking omeprazole without speaking to your doctor first.3
  • The delayed-release tablets should not be crushed, but swallowed whole.12
  • If you struggle to swallow the capsules, you can open them and mix the contents into apple sauce before swallowing. Speak to your doctor before doing this.12
  • If you miss one of your doses, do not take two doses at the same time to make up for the previous one. Take the missed dose as soon as you remember, but if it is almost time for the next dose, then rather wait.12

Tell your doctor or pharmacist about:

  • Any allergies you have to the ingredients in omeprazole or similar medications (Dexilant, Nexium, Prevacid or Protonix). Ask them for the list of ingredients in the omeprazole product if you are unsure.12
  • Any prescription or non-prescription medications you are currently taking.12
  • Any nutritional, vitamin and mineral supplements you are taking.12
  • Any herbal products or medications you are taking.12
  • Any times in your life where you have had low magnesium levels or liver problems.3

If you have had frequent heart burn for more than three months and want to try taking non-prescription omeprazole, it is a good idea to let your doctor know beforehand if you have any of the following symptoms with the heart burn:

  • Dizziness, light-headedness or shortness of breath
  • Pain in your shoulders or chest
  • Pain that spreads from your chest to your arms, neck and shoulders
  • Stomach pain
  • Painful or difficult swallowing
  • Nausea, vomiting or unintentional weight loss
  • Blood in your stools or vomit.12

These symptoms could mean that you have a more serious condition which needs extra medical support.

Warnings for Special Groups

If you fall into the following groups of people, you may need to take special precautions before using omeprazole:

  • If you are fifty years or older, you are at a higher risk of getting diarrhoea from difficile infection and you are also at a higher risk of getting bone fractures. Your doctor may put you on a lower dosage and will need to monitor your side effects carefully.12
  • If you are pregnant or planning on falling pregnant, let your doctor know. It is not yet known whether omeprazole is harmful to your developing baby or not. Your doctor will be able to help you weigh up the risks versus the benefits.3,12
  • If you are breastfeeding, omeprazole can pass through breastmilk to your baby. Your doctor will be able to tell you how to breastfeed safely when taking omeprazole.12

Storage of Omeprazole

It is important to store omeprazole at the correct temperatures to prevent it from being damaged:

  • Delayed-release capsules should be stored between 59°F to 86°F (15°C to 30°C).
  • Delayed-Release oral suspension granules should be stored between 68°F to 77°F (20°C to 25°C).3

Make sure that the containers of omeprazole are sealed tightly between usage, kept dry and away from light. Always make sure that omeprazole is kept well out of reach of children.3

Omeprazole (Prilosec) Drug Interactions

Omeprazole interacts with certain medications, decreasing their effectiveness and absorption. Sometimes these interactions between omeprazole and other drugs can also cause worse side effects.12 If you are taking any of the following medications, let your doctor know:

  • Antibiotics, such as ampicillin (Principen, Unasyn)
  • Ketoconazole
  • Diuretics
  • Cilostazol (Pletal)
  • Anticoagulants (blood thinners), such as warfarin (Coumadin)
  • Atazanavir (Reyataz)
  • Iron supplements
  • Cyclosporine (Neoral, Sandimmune)
  • Digoxin (Lanoxicaps, Lanoxin), disulfiram (Antabuse)
  • Benzodiazepines, such as diazepam (Valium)
  • Clopidogrel (plavix)
  • Methotrexate (rheumatrex, trexall)
  • Nelfinavir (viracept)
  • Voriconazole (vfend)
  • Saquinavir (invirase)
  • Antifungal or anti-yeast medications
  • Phenytoin (dilantin)
  • Tacrolimus (prograf)3,12


Omeprazole (Prilosec) Compared to Other Similar Drugs

Omeprazole is not the only Proton Pump Inhibitor (PPI) on the market.  There are many other PPIs with similar effects, so how do you choose which one to use?

Omeprazole vs Esomeprazole

Esomeprazole (Nexium) is very similar on a chemical level to omeprazole, just with a slightly different arrangement of its atoms.5,8 This causes it to have slightly different effects on your body:

  • It can cause your stomach to make even less stomach acid than omeprazole This means that it could help to relieve your heart burn symptoms more.5
  • It is also able to kill pylori bacteria more effectively than omeprazole.8

The disadvantages of Nexium are that it is more expensive than omeprazole and may have slightly more side effects.  It is best to speak to your doctor to weigh up which medication would be better for you personally.5,8

Omeprazole vs Pantoprazole

Pantoprazole (Protonix) is very similar to omeprazole. It has an equal effect on the stomach and how much acid it makes. There is not a big difference in its effectiveness, cost or safety.2,11

Omeprazole vs Famotidine

Famotidine (Pepcid) also works very similarly to omeprazole, but there is a slight chance that omeprazole may work better at decreasing the amount of acid your stomach makes. This is only true if you do not have H. pylori infection though. If you do have H. pylori infection, then famotidine is equally effective and safe to use.4

Omeprazole vs Ranitidine (Zantac)

Ranitidine (Zantac) is another common PPI used to treat heart burn.  Like omeprazole, it is available in a non-prescription and prescription form.  There is no big difference in its ability to decrease stomach acid, although, omeprazole might be better at preventing relapses than ranitidine.7,11

If you are taking Non-Steroidal Anti-Inflammatory Drugs (NSAIDS), omeprazole could be more effective than ranitidine for you. 11

When choosing which PPI to use, it is very important to note that they all have different side effects, drug interactions and medical conditions they may cause problems with.  Always speak to your doctor or pharmacist before changing between PPIs.

Abuses of Omeprazole

It is not common for omeprazole to become addictive, as it has no “mind-altering” effects, but it is possible that you could become dependent on using it to control your heartburn. If your heartburn persists for longer than the suggested length of treatment, you need to tell your doctor. It is important to follow the dose guidelines and to not exceed the suggested dose or duration of treatment. If you take more omeprazole than suggested, you will be at greater risk of developing the side effects mentioned above.3,12

It is possible to overdose on omeprazole if you take more than 900mg at one time.12 Signs of omeprazole overdose include:

  • Confusion
  • Dizziness
  • Flushing
  • Dry mouth
  • Nausea
  • Blurred vision
  • Headache
  • Pounding or very fast heartbeat
  • Sweating3,12

An omeprazole overdose is unlikely to be fatal, but it is still very important to call your local poison control center at 1-800-222-1222. If the symptoms are severe or the person is unconscious or not breathing, phone 911.3,12


Other Important Information

Make sure that you do not miss any appointments with your doctor. Tell them about any side effects you are experiencing. Your doctor may need to do further medical tests if omeprazole is not working effectively or if you are experiencing side effects, especially diarrhoea.3,12

If you go into hospital for any reason, even for minor surgeries, make sure that you give the doctor, surgeon or dentist a list of all the medications you are taking, as well as any vitamin, mineral or herbal supplements.12


Omeprazole (Prilosec) FAQs

– Is omeprazole a PPI?

  • Omeprazole is a Proton Pump Inhibitor (PPI).
  • PPIs act on the cells in the lining of the stomach, causing them to make less stomach acid.1,3,12


– Can you take omeprazole while pregnant?

  • The safety of using omeprazole during pregnancy is not yet known.
  • It is possible that omeprazole could pass through the placenta to your baby.
  • Talk to your doctor before going on omeprazole treatment if you are pregnant or breastfeeding.3,12


– Can omeprazole cause you to gain weight?

  • While you are living with heart burn, you may need to avoid certain foods (especially those high in fat, such as fried foods) or eat smaller meals.
  • Once you start taking omeprazole, and your heart burn decreases, you may find that you begin to eat larger meals and fattier foods.
  • It is possible that this could lead to weight gain.
  • Weight gain could also be caused by swelling of your body, as a side effect of taking omeprazole. If you notice sudden or unexplained weight gain, talk to you doctor.14


– Does omeprazole cause dry mouth?

  • Omeprazole can cause dry mouth, but it is not common and usually goes away once treatment has been stopped.12


– Does omeprazole cause hair loss?

  • Omeprazole can cause hair loss occasionally, but it is not common and isn’t usually severe.12


– Can omeprazole cause more heartburn?

  • This is unlikely if it is taken correctly.
  • If you find that you do get more heartburn, this could indicate that you have a more serious condition.
  • It is best to let your doctor know if this happens.12


– Is omeprazole safe?

  • Omeprazole is safe, as long as you follow the suggested guidelines for usage and do not exceed the recommended dose or duration.3,12


– When is the best time to take omeprazole?

  • This depends on the condition that you have, but generally, omeprazole is taken once every day in the morning. It is always taken at least one hour before eating food.12



  1. Achem SR, Kolts BE, Macmath T, Richter J, Mohr D, Burton L, Castell DO. Effects of omeprazole versus placebo in treatment of noncardiac chest pain and gastroesophageal reflux. Digestive diseases and sciences. 1997 Oct 1; 42(10):2138-45.
  2. Cuisset T, Frere C, Quilici J, Poyet R, Gaborit B, Bali L, Bonnet JL. Comparison of omeprazole and pantoprazole influence on a high 150-mg clopidogrel maintenance dose. Journal of the American College of Cardiology 2009; 54(13): 1149-1153.
  3. Food and Drug Association. MEDICATION GUIDE PRILOSEC® (pry-lo-sec) (omeprazole) delayed-release capsules PRILOSEC (pry-lo-sec) (omeprazole magnesium) for delayed-release oral suspension 2016.
  4. Fujiwara Y, Higuchi K, Nebiki H, Chono S, Uno H, Kitada K, Satoh H, Nakagawa K, Kobayashi K, Tominaga K, Watanabe T. Famotidine vs. omeprazole: a prospective randomized multicentre trial to determine efficacy in non‐erosive gastro‐oesophageal reflux disease. Alimentary pharmacology & therapeutics. 2005 Jun 1; 21(s2):10-8.
  5. Gatta L, Perna F, Figura N, Ricci C, Holton J, D’anna L, Miglioli M, Vaira D. Antimicrobial activity of esomeprazole versus omeprazole against Helicobacter pylori. Journal of Antimicrobial Chemotherapy. 2003 Feb 1; 51(2):439-42.
  6. Gilard M, Arnaud B, Cornily JC, Le Gal G, Lacut K, Le Calvez G, Mansourati J, Mottier D, Abgrall JF, Boschat J. Influence of omeprazole on the antiplatelet action of clopidogrel associated with aspirin. Journal of the American College of Cardiology. 2008 Jan 22;51(3):256-60.
  7. Havelund T, Laursen LS, Skoubo-Kristensen E, Andersen BN, Pedersen SA, Jensen KB, Fenger C, Hanberg-Sørensen F, Lauritsen K. Omeprazole and ranitidine in treatment of reflux oesophagitis: double blind comparative trial. Br Med J (Clin Res Ed). 1988 Jan 9; 296(6615):89-92.
  8. Lind T, Kyleback A, Rydberg L, Jonsson A, Andersson T, Hasselgren G, Rohss K. Esomeprazole provides improved acid control vs omeprazole in patients with symptoms of GERD. Gastroenterology. 2000 Apr 1; 118(4):A18.
  9. Mcarthur KE, Collen MJ, Maron PN, Cherner JA, Howard JM, Ciarleglio CA, Cornelius MJ, Jensen RT, Gardner JD. Omeprazole: Effective, Convenient Therapy for Zollinger—Ellison Syndrome. Gastroenterology. 1985 Apr 30; 88(4):939-44.
  10. McGowan CC, Cover TL, Blaser MJ. The proton pump inhibitor omeprazole inhibits acid survival of Helicobacter pylori by a urease-independent mechanism. 1994 Nov 1;107(5):1573-8.
  11. Mössner J, HERZ R, Schneider A. A double‐blind study of pantoprazole and omeprazole in the treatment of reflux oesophagitis: a multicentre trial. Alimentary pharmacology & therapeutics. 1995 Jun 1; 9(3):321-6.
  12. National Institute of Health. Omperazole, last revised 07/15/2016.
  13. Yeomans ND, Tulassay Z, Juhász L, Rácz I, Howard JM, Van Rensburg CJ, Swannell AJ, Hawkey CJ. A comparison of omeprazole with ranitidine for ulcers associated with nonsteroidal antiinflammatory drugs. New England Journal of Medicine. 1998 Mar 12; 338(11):719-26.
  14. Yoshikawa I, Nagato M, Yamasaki M, Kume K, Otsuki M. Long-term treatment with proton pump inhibitor is associated with undesired weight gain. World journal of gastroenterology: WJG 2009 Oct 14;15(38):4794.
  15. Young SY, Omeprazole prescription bottle with side effects info sheet.


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