Omeprazole is in a class of drugs called proton pump inhibitors (PPI) that block the production of acid by the stomach. Other drugs in the class include lansoprazole (Prevacid), rabeprazole (Aciphex), pantoprazole (Protonix), and esomeprazole (Nexium). Proton pump inhibitors are used for the treatment of conditions such as ulcers, gastroesophageal reflux disease (GERD) and the Zollinger-Ellison syndrome, which are all caused by stomach acid. Omeprazole, like other proton-pump inhibitors, blocks the enzyme in the wall of the stomach that produces acid. By blocking the enzyme, the production of acid is decreased, and this allows the stomach and esophagus to heal. Zegerid contains omeprazole and an antacid (sodium bicarbonate). The FDA approved omeprazole in September 1989.

Prilosec, Zegerid, Prilosec OTC, Zegerid OTC

GENERIC AVAILABLE: Yes (Prilosec)

Yes; No (Prilosec OTC, Zegerid OTC)

Omeprazole like other PPIs is well-tolerated. The most common side effects are:

• diarrhea,
• nausea,
• vomiting,
• headaches,
• rash and
• dizziness.

Other important side effects include:

• Nervousness,
• abnormal heartbeat,
• muscle pain,
• weakness,
• leg cramps, and water retention occur infrequently.

Each packet of Zegerid powder for oral suspension contains 460 mg of sodium and each capsule contains 304 mg of sodium. This should be taken into consideration in patients who need a sodium restricted diet.

Proton pump inhibitors may increase the risk of Clostridium difficile infection. High doses and long-term use (1 year or longer) may increase the risk of osteoporosis-related fractures of the hip, wrist, or spine. Prolonged use also reduces absorption of vitamin B12 (cyanocobalamin).

Long-term use of PPIs has also been associated with low levels of magnesium (hypomagnesemia). Analysis of patients taking PPIs for long periods of time showed an increased risk of heart attacks.

Therefore, it is important to use the lowest doses and shortest duration of treatment necessary for the condition being treated.

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.

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).

Use of omeprazole in pregnant women has not been adequately evaluated. Omeprazole should be used during pregnancy only if the benefits justify the unknown risks.

Omeprazole is excreted in breast milk and potentially could cause adverse effects in the infant.

What preparations of omeprazole are available?

Capsules: 10, 20 and 40 mg. Tablets: 20 mg (Prilosec OTC). Powder for oral suspension: 20 and 40 mg

How should I keep omeprazole stored?

Capsules should be stored at 15 to 30 C (59 to 86 F) and tablets at 20 to 25 C (68 to 77 F). They should be kept away from moisture and light.