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Omeprazole

Common Brand Names: Prilosec

Drug Information

Medically reviewed by Jessica Swirble, PharmD
Last updated on April 17, 2025

Drug Information | Side Effects | Use & Dosage | Request an Online Prescription

Quick facts

  • Brand Name: Prilosec
  • Generic Name: Omeprazole
  • Uses: Treating gastroesophageal reflux disease (GERD), stomach ulcers, and conditions where the stomach produces too much acid, such as Zollinger-Ellison syndrome
  • Drug Class: Proton pump inhibitor (PPI)
  • Availability: Prescription only; also available over-the-counter for specific conditions
  • Generic Status: Yes
  • Controlled Substance: No

What is omeprazole?

Omeprazole is a proton pump inhibitor used primarily to reduce stomach acid production. It works by blocking a specific system within the stomach lining that secretes acid into the stomach. This helps to prevent and heal acid-related damage to the stomach and esophagus and helps reduce symptoms of heartburn and acid reflux.

What conditions does omeprazole treat?

Omeprazole is primarily used to treat conditions such as:

  • Gastroesophageal reflux disease (GERD): Omeprazole relieves GERD symptoms, such as heartburn and acid reflux, and promotes healing of erosive esophagitis.
  • Stomach ulcers: Omeprazole prevents and treats ulcers, especially those caused by nonsteroidal anti-inflammatory drugs (NSAIDs).
  • Excessive stomach acid conditions: Such as Zollinger-Ellison syndrome, where omeprazole helps to manage the symptoms by reducing stomach acid production.

It is also used in combination with antibiotics to treat and prevent the recurrence of stomach ulcers caused by Helicobacter pylori.

How does omeprazole work?

Omeprazole works by irreversibly blocking the proton pump, a key component in the acid secretion mechanism of the gastric parietal cells in the stomach. This leads to a significant reduction in stomach acid output.

How do I take omeprazole?

Omeprazole can be taken in different forms, depending on specific needs:

  • Oral capsules or tablets: Typically taken once daily, 30 minutes before a meal.
  • Oral packet: Mixed with water, usually once a day.

The dosage and duration of treatment depend on the condition being treated, its severity, and your response to the medication.

Follow your healthcare provider's instructions regarding dosage and schedule. Do not exceed the prescribed dose or duration of treatment without consulting your provider.

How long until I feel better?

The effectiveness of omeprazole and the time it takes to notice improvement can vary among individuals. Symptom relief, such as reduced heartburn or acid reflux, can be observed within one to two days of starting the medication, but it may take up to four weeks for full therapeutic benefits, especially for healing ulcers or erosive esophagitis.

Continue taking omeprazole as prescribed even if you start feeling better. Do not abruptly stop the medication without consulting your healthcare provider.

Are there any other uses for omeprazole?

While omeprazole is primarily used for managing acid-related disorders, healthcare providers may sometimes prescribe it off-label for conditions such as:

  • Laryngopharyngeal reflux (LPR)
  • Prevention of stress ulcers in critically ill patients

Discuss any alternative uses of omeprazole with your healthcare provider.

Dosage forms of omeprazole

Omeprazole is available in the following dosage forms:

  • Oral capsules: Typically available in 10mg, 20mg, 40mg dosages.
  • Oral tablets: Available for over-the-counter use, typically in 20mg dosages.
  • Oral packet (powder to be mixed with water): 2.5mg and 10mg dosages.

Generic versions of omeprazole are available, providing cost-effective treatment options.

Omeprazole is a prescription medication, although certain dosages and forms may be available over the counter. You will need a valid prescription from a licensed healthcare provider to obtain higher dosage forms of this medication.

Side Effects and Precautions for Omeprazole


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What are the side effects of omeprazole?

The use of omeprazole can lead to various side effects in some individuals.

Common mild side effects of omeprazole use include:

  • Headache
  • Diarrhea or constipation
  • Nausea or upset stomach
  • Vomiting
  • Gas or bloating
  • Dizziness
  • Rash
  • Cough

More severe side effects of omeprazole use can include:

  • Severe stomach pain, nausea, or vomiting
  • Kidney problems (such as changes in urine output)
  • Severe diarrhea, especially if it is watery or bloody
  • Unusual weight gain or swelling
  • Low magnesium levels (leading to rapid heartbeat, jitteriness, muscle cramps, muscle spasms, or weakness)
  • Lupus-like symptoms (such as rash on the nose and cheeks, new or worsening joint pain)

If you experience any severe or concerning side effects while taking omeprazole, contact your healthcare provider right away.

What should I tell my healthcare provider before using omeprazole?

Tell your healthcare provider about any existing medical conditions, allergies, or other medications you are taking before starting treatment with omeprazole. This includes prescription drugs, over-the-counter medications, and dietary supplements, as they may interact with omeprazole.

Tell your provider if you are taking these medications or supplements:

  • Anticoagulants (such as warfarin)
  • Antiplatelet medications
  • Antifungal medications
  • Antibiotics
  • HIV medications
  • Anti-seizure medications
  • Medications for depression
  • Other stomach acid reducers
  • Iron supplements
  • St John’s wort

You should also mention medical conditions such as:

  • Liver disease
  • Osteoporosis or low bone mineral density
  • Low magnesium or vitamin B12 levels
  • Autoimmune disorders such as lupus
  • Stomach cancer

If you are pregnant, planning to become pregnant, or breastfeeding, consult your healthcare provider before using omeprazole to assess potential risks and benefits.

Are there any other special instructions I should follow?

Take omeprazole exactly as prescribed by your healthcare provider. Do not exceed the recommended dose or duration of treatment.

Omeprazole should be taken before meals, preferably in the morning. Swallow the capsules whole; do not crush, chew, or open them.

Avoid alcohol and foods that may trigger your symptoms. Be mindful of your body’s response to different dietary choices and activities.

Store omeprazole at room temperature, away from moisture and heat. Keep it out of reach of children.

What should I do in case of an overdose?

In case of an omeprazole overdose, seek medical attention immediately. Symptoms of overdose may include confusion, drowsiness, blurred vision, fast or pounding heartbeats, nausea, vomiting, sweating, flushing, headache, dry mouth, and a faint feeling. If you suspect an overdose, contact the poison control helpline at 1-800-222-1222 or call emergency services.

Proper Use & Dosage Information for Omeprazole


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What is the typical starting dose for omeprazole?

Omeprazole is available in the following forms:

  • Oral capsules (10 mg, 20 mg, 40 mg)
  • Oral packet (2.5mg and 10mg)
  • Oral tablets (over-the-counter: 20 mg)

The typical starting dose of omeprazole varies depending on the condition being treated, the severity of symptoms, and individual patient factors. It is important to follow your healthcare provider's instructions regarding dosage and administration.

For gastroesophageal reflux disease (GERD), the typical starting dose may be:

  • Oral capsules: 20 mg, once daily.

The dosage may be adjusted based on the response and tolerance to the medication. Your healthcare provider will determine the most appropriate dose based on your medical history, current medications, and response to the medication.

Omeprazole should be taken exactly as prescribed by your healthcare provider. Do not exceed the recommended dose or duration of treatment without consulting your provider.

If you have any questions about your dosage or need adjustments, contact your healthcare provider for guidance. If you want to talk to a provider right away, consider scheduling an online doctor appointment through a platform like Sesame.

What should I do if I miss a dose of omeprazole?

If you miss a dose of omeprazole, take it as soon as you remember unless it is close to the time for your next scheduled dose. In that case, skip the missed dose and continue with your regular dosing schedule. Do not double the dose to make up for a missed one.

Maintain a consistent dosing schedule to ensure the effectiveness of omeprazole in managing your condition.

What should I do if I'm feeling better while taking omeprazole?

Continue taking omeprazole as prescribed by your healthcare provider, even if you start feeling better. Do not stop the medication abruptly without consulting your provider, as it may lead to a recurrence of symptoms or other complications.

Complete the full course of treatment as directed to minimize the risk of relapse.

If you have any concerns or questions about your medication, discuss them with your healthcare provider for personalized guidance and recommendations.

How should I store omeprazole?

Store omeprazole according to the instructions provided by your healthcare provider or pharmacist. Keep it at room temperature, away from moisture, heat, and light. Ensure the container is tightly closed and out of reach of children.

Do not use expired medication or medications that appear damaged or discolored. If you have any questions about storage, consult your healthcare provider or pharmacist for guidance.

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