Omeprazole is used to treat certain stomach and esophagus problems (such as acid reflux, ulcers). It works by decreasing the amount of acid your stomach makes. It relieves symptoms such as heartburn, difficulty swallowing, and cough. This medication helps heal acid damage to the stomach and esophagus, helps prevent ulcers, and may help prevent cancer of the esophagus. Omeprazole belongs to a class of drugs known as proton pump inhibitors (PPIs).

If you are self-treating with this medication, over-the-counter omeprazole products are used to treat frequent heartburn (occurring 2 or more days a week). Since it may take 1 to 4 days to have full effect, these products do not relieve heartburn right away.

For over-the-counter products, carefully read the package instructions to make sure the product is right for you. Check the ingredients on the label even if you have used the product before. The manufacturer may have changed the ingredients. Also, products with similar brand names may contain different ingredients meant for different purposes. Taking the wrong product could harm you.

If your doctor has prescribed this medication for you, read the Patient Information Leaflet if available from your pharmacist before you start taking omeprazole and each time you get a refill. If you are taking the over-the-counter product to self-treat, read and follow all directions on the product package before taking this medication.

Take this medication by mouth as directed, usually once daily before a meal. The dosage and length of treatment are based on your medical condition and response to treatment. Children's dosage is also based on weight. Do not increase your dose or take this drug more often than directed. If you have any questions, ask your doctor or pharmacist.

Do not crush, break, or chew delayed release tablets. Doing so can release all of the drug at once, increasing the risk of side effects.

If you are using the disintegrating delayed release tablets, use dry hands to handle the tablets. Place the tablet on your tongue and let it dissolve. After the tablet has dissolved, it can be swallowed with or without water. The tablets can also be swallowed whole with water.

If needed, antacids may be taken along with this medication. If you are also taking sucralfate, take omeprazole at least 30 minutes before sucralfate.

Use this medication regularly to get the most benefit from it. To help you remember, take it at the same time each day. Continue to take this medication for the prescribed length of treatment even if you are feeling better. If you are self-treating with the over-the-counter product, do not take it for more than 14 days unless directed by your doctor.

Tell your doctor if your condition lasts or gets worse. If you are self-treating, tell your doctor if your heartburn lasts after 14 days or if you need to use this medication more than once every 4 months. The risk of side effects goes up over time. Ask your doctor how long you should take this medication. If you think you may have a serious medical problem, get medical help right away.

See also Precautions section.

Headache or abdominal pain may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

If your doctor has directed you to use this product, remember that your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• symptoms of a low magnesium blood level (such as muscle spasms, irregular heartbeat, seizures)
• signs of lupus (such as rash on nose and cheeks, new or worsening joint pain)
• signs of kidney problems (such as change in the amount of urine, pink/bloody urine)

This medication may rarely cause a severe intestinal condition due to a bacteria called C. difficile. This condition may occur during treatment or weeks to months after treatment has stopped. Tell your doctor right away if you develop:

• diarrhea that doesn't stop
• abdominal or stomach pain/cramping
• blood/mucus in your stool

If you have these symptoms, do not use anti-diarrhea or opioid products because they may make symptoms worse.

Rarely, proton pump inhibitors (such as omeprazole) have caused vitamin B-12 deficiency. The risk is increased if they are taken every day for a long time (3 years or longer). Tell your doctor right away if you develop symptoms of vitamin B-12 deficiency (such as unusual weakness, sore tongue, or numbness/tingling of the hands/feet).

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• fever
• swollen lymph nodes
• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking omeprazole, tell your doctor or pharmacist if you are allergic to it; or to similar drugs (such as esomeprazole, lansoprazole, pantoprazole); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• liver disease
• lupus

Some symptoms may actually be signs of a more serious condition. Get medical help right away if you have:

• heartburn with lightheadedness/sweating/dizziness
• chest/jaw/arm/shoulder pain (especially with shortness of breath, unusual sweating)
• unexplained weight loss

In addition, before you self-treat with this medication, get medical help right away if you have any of these signs of a serious condition:

• trouble/pain swallowing food
• bloody vomit
• vomit that looks like coffee grounds
• bloody/black stools
• heartburn for over 3 months
• frequent chest pain
• frequent wheezing (especially with heartburn)
• nausea/vomiting
• stomach pain

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Proton pump inhibitors (such as omeprazole) may increase your risk for bone fractures, especially with longer use, higher doses, and in older adults. Talk with your doctor or pharmacist about ways to prevent bone loss/fracture, such as by taking calcium (such as calcium citrate) and vitamin D supplements.

Older adults may be more sensitive to the side effects of this drug, especially bone loss and fractures (see above), and C. difficile infection (see Side Effects section).

Children may be more sensitive to the side effects of this drug, especially fever, cough, and infections of the nose/throat/airways.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.

This medication passes into breast milk. The effects on a nursing infant are unknown. Consult your doctor before breastfeeding.

See also How to Use section.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug include:

• clopidogrel
• mavacamten
• methotrexate (especially high-dose treatment)
• rifampin
• St John's wort

Some products need stomach acid so that the body can absorb them properly. Omeprazole decreases stomach acid, so it may change how well these products work. Some affected products include atazanavir, erlotinib, levoketoconazole, nelfinavir, pazopanib, rilpivirine, sparsentan, certain azole antifungals (itraconazole, ketoconazole, posaconazole), among others.

Omeprazole is very similar to esomeprazole. Do not use any medications containing esomeprazole while using omeprazole.

This medication may interfere with certain lab tests, possibly causing false test results. Make sure lab personnel and all your doctors know you use this drug.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669. Symptoms of overdose may include: confusion, unusual sweating, blurred vision, unusually fast heartbeat.

If your doctor has prescribed this medication for you, do not share it with others.

If your doctor instructs you to use this medication regularly for a long time, lab and/or medical tests (such as a magnesium blood test, vitamin B-12 levels) may be done while you are taking this medication. Keep all medical and lab appointments. Consult your doctor for more details.

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.