omeprazole, omeprazole/sodium bicarbonate, Prilosec, Zegerid, Prilosec OTC, Zegerid OTC

  • Pharmacy Author:
    Omudhome Ogbru, PharmD

    Dr. Ogbru received his Doctorate in Pharmacy from the University of the Pacific School of Pharmacy in 1995. He completed a Pharmacy Practice Residency at the University of Arizona/University Medical Center in 1996. He was a Professor of Pharmacy Practice and a Regional Clerkship Coordinator for the University of the Pacific School of Pharmacy from 1996-99.

  • Medical and Pharmacy Editor: Jay W. Marks, MD
    Jay W. Marks, MD

    Jay W. Marks, MD

    Jay W. Marks, MD, is a board-certified internist and gastroenterologist. He graduated from Yale University School of Medicine and trained in internal medicine and gastroenterology at UCLA/Cedars-Sinai Medical Center in Los Angeles.

What is the dosage for omeprazole?

For ulcers, GERD, erosive esophagitis and eradication of H. pylori the recommended dose for adults is 20-40 mg daily. Ulcer healing usually occurs within 4-8 weeks.

H. pylori infections are treated for 10-28 days.

The usual dose for prevention of upper gastrointestinal bleeding in critically ill patients is 40 mg daily for 14 days.

Prilosec OTC is used for treating heartburn for up to two weeks, and the usual dose is 20 mg daily.

For the management of Zollinger-Ellison Syndrome the starting dose for adults is 60 mg daily, and the dose is adjusted based on either the response of symptoms or the actual measurement of acid production. Doses greater than 80 mg should be divided. Doses up to 120 mg three times a day have been used in the treatment of Zollinger-Ellison Syndrome.

For maximal efficacy, omeprazole tablets should be taken before meals, swallowed whole and should not be crushed, chewed or opened.

Which drugs or supplements interact with omeprazole?

Omeprazole potentially can increase the concentrations in blood of diazepam (Valium), warfarin (Coumadin), and phenytoin (Dilantin) by decreasing the elimination of these drugs by the liver.

The absorption of certain drugs may be affected by stomach acidity. Therefore, omeprazole as well as other PPIs reduce the absorption and concentration in blood of ketoconazole (Nizoral) and increase the absorption and concentration in blood of digoxin (Lanoxin). This may reduce the effectiveness of ketoconazole or increase digoxin toxicity.

Through unknown mechanisms, omeprazole may increase blood levels of saquinavir and reduce blood levels of nelfinavir and atazanavir, drugs that are used for treating patients with infection caused by the human immunodeficiency virus (HIV). Accordingly, the dose of saquinavir may need to be reduced to avoid toxicity, and the doses of nelfinavir and atazanavir may need to be increased to maintain efficacy.

Clopidogrel (Plavix) is converted to its active form by enzymes in the liver. Omeprazole reduces the activity of these enzymes and potentially can reduce the activity of clopidogrel. Omeprazole should not be used with clopidogrel.

Omeprazole increases the concentration of cilostazol (Pletal). The dose of cilostazol should be reduced from 100 mg twice daily to 50 mg twice daily when given with omeprazole.

Omeprazole may increase blood levels of methotrexate (Rheumatrex, Trexall) and tacrolimus (Prograf).

Medically Reviewed by a Doctor on 7/1/2015

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