Mar Vista Animal Medical Center

3850 Grand View Blvd.
Los Angeles, CA 90066




(for veterinary information only)




(10 mg, 20 mg, 40 mg)



The quest for medications against nausea and upset stomach is on-going in both human and veterinary medicine. In the past, antacids started as simple alkaline products that one swallowed to neutralize stomach acid. As the production of stomach acids came to be better understood, antacids that interfered with actual acid production were developed. The H2 blocking drugs were developed next. H2 blockers get their name because they block H2 receptors, special receptors for histamine in the stomach that when stimulated would cause stomach acid production. Blocking the receptor meant blocking acid production. Cimetidine (Tagamet®) was the first H2 blocker released followed by ranitidine (Zantac®) and famotidine (Pepcid AC®). It turns out, however, that there are other receptors involved in stomach acid secretion besides H2 receptors so even with H2 receptors blocked, acid could still be secreted. This is where omeprazole comes in.

Omeprazole represents a different tact: proton pump inhibition. The quantity of acid secreted ultimately amounts to the quantity of protons pumped. The proton pump is central to secreting acid into the stomach and with this pump inhibited, stomach acid production is halted. Proton pump inhibitors like omeprazole are the strongest antacids of all. They work not only when the stomach is full/digesting food but all the time.



Omeprazole is used in the treatment of stomach ulcers or in the prevention of stomach ulcers. Relatedly, omeprazole is commonly used as part of "triple therapy" against the ulcer-causing stomach bacteria known as Helicobacter. Omeprazole is generally used once a day though it can take 3-5 days to achieve maximum effect. Omeprazole is best given on an empty stomach before the first meal of the day but may be given with food if necessary.

If a dose is accidentally skipped, simply give it when it is remembered and time the next dose accordingly.




Increases in liver enzymes may be induced by the use of omeprazole. This is not harmful but should be recognized as an omeprazole reaction should it be seen on a blood test.

Side effects of omeprazole include appetite loss, gas, and diarrhea but these are generally mild.

Omeprazole is able to reduce cerebrospinal fluid production though it is not known how. While this is listed as a side effect, it could be the desired primary effect if used in patients with hydrocephalus or syringomyelia where reduced cerebrospinal fluid pressure is the goal.




Omeprazole inhibits a system of liver enzymes called the “cytochrome p450 system.” Many other drugs depend on this system for removal. This means that if omeprazole is used, the following drugs will last longer and work more strongly: benzodiazepine tranquilizers (diazepam, alprazolam etc.), phenytoin (used to treat both seizures and heart rhythm disturbances), and warfarin (a blood thinning agent).

Because omeprazole reduces stomach acid, other drugs that require an acid environment for absorption into the body may not be as well absorbed. Such drugs include ketoconazole (an antifungal agent), and some forms of ampicillin (an antibiotic).

Blood levels of cyclosporine, an immunomodulator, may be increased with concurrent use of omeprazole.

Clopidogrel, a blood thinner, may not be activated properly if used concurrently with omeprazole. It may be best to use a different antacid.



Omeprazole should be stored at room temperature in a light-tight container.

If the pet is reluctant to swallow the capsules, do not attempt to crush the pellets inside the capsules and add them to water or food. It is permissible to add them to fruit juice, however.

Omeprazole is removed from the body by both the liver and kidneys. The dosage of omeprazole should be altered if the patient suffers from either liver or kidney insufficiency.

Safety of the use of this medication in lactation or pregnancy has not been established.

Omeprazole requires 3-5 days to achieve maximum effect in dogs. Feline information on timing are lacking at this time.

Four weeks of use is considered safe for cats and dogs but such extreme stomach acid reduction for longer than this period is controversial.


Short version (to help us comply with "Lizzie's Law")

Page last revised: 9/4/2020