It is a human medicine. A vet may still prescribe it for a dog or cat, which is legal and common, but it means no company has proved to the FDA that it works or is safe in that animal, and there is no approved animal dose to look up. Ask your vet what they expect it to do and what to watch for.
The label says, word for word:
Human label: "PRILOSEC is indicated for short-term treatment of active duodenal ulcer in adults." (other label indications: Helicobacter pylori Eradication; Treatment of Active Benign Gastric Ulcer; Treatment of Symptomatic GERD; Treatment of Erosive Esophagitis Due to Acid-Mediated GERD; Maintenance of Healing of EE Due to Acid-Mediated GERD; Pathological Hypersecretory Conditions).
PRILOSEC is contraindicated in patients with known hypersensitivity to substituted benzimidazoles or to any component of the formulation. Hypersensitivity reactions may include anaphylaxis, anaphylactic shock, angioedema, bronchospasm, acute tubulointerstitial nephritis, and urticaria. Proton pump inhibitors (PPIs), including PRILOSEC, are contraindicated in patients receiving rilpivirine-containing products.
In adults, symptomatic response to therapy with PRILOSEC does not preclude the presence of gastric malignancy.
Acute tubulointerstitial nephritis (TIN) has been observed in patients taking PPIs and may occur at any point during PPI therapy.
Published observational studies suggest that PPI therapy like PRILOSEC may be associated with an increased risk of Clostridium difficile-associated diarrhea, especially in hospitalized patients.
Several published observational studies suggest that proton pump inhibitor (PPI) therapy may be associated with an increased risk for osteoporosis-related fractures of the hip, wrist, or spine.
PPI use is associated with an increased risk of fundic gland polyps that increases with long-term use, especially beyond one year.
Every approved medicine has a field study behind it, and the label prints what happened:
Human label: "The most common adverse reactions reported (i.e., with an incidence rate ≥2%) from PRILOSEC-treated patients enrolled in these studies included headache (7%), abdominal pain (5%), nausea (4%), diarrhea (4%), vomiting (3%), and flatulence (3%)."
Omeprazole (Prilosec) is a human drug; the prescription label used is "PRILOSEC® (omeprazole magnesium) for delayed-release oral suspension" (Covis Pharma US, Inc; no AstraZeneca Prilosec label is on DailyMed). Prilosec OTC (The Procter & Gamble Manufacturing Company) is a separate over-the-counter human product.
The emergency page sorts the signs by how long you have, and the symptom checker asks what you are seeing. Reactions to a medicine can also be reported to the FDA yourself: how to report a problem.
These answers come from the approved label on DailyMed, read on 2 October 2026. Where the label does not say, the answer says so, and the vet or the pharmacist is the one to ask.
The approved use is quoted at the top of this page. The label read for these answers is the one for PRILOSEC, a human prescription medicine that lowers the acid the stomach makes. It is approved for ulcers and acid reflux disease in people and does not mention dogs or cats, so ask the vet what it has been prescribed for in your pet.
The label gives no time for a pet. In people, it says the acid-lowering effect starts within one hour of a dose by mouth and is greatest within two hours. With one dose a day, it says the effect builds up and levels off after four days.
The label read here is for packets of granules, and its directions and doses are written for people. The granules are stirred into water, left for 2 to 3 minutes to thicken, stirred again and drunk within 30 minutes, and the label says to take the medicine before meals. If your pet's omeprazole is a capsule or a tablet, those mixing directions do not apply to it, so follow the vet's instructions and ask the pharmacist about anything they leave open.
The label is written for people. It says to take a missed dose as soon as possible, unless the next dose is already due. In that case the missed dose is left out and the next one is taken on time. It says not to take two doses at once to make up for the missed one. Ask the vet or the pharmacist whether the same goes for your pet.
The studies and the warnings are quoted above. This label is written for people. Its Medication Guide tells patients to stop the medicine and call the doctor right away at the first sign of a severe skin reaction. It also tells them to call the doctor right away if they pass less urine or have blood in the urine, or if they have watery stools or stomach pain that does not go away. The same goes for new or worsening joint pain, or a rash on the cheeks or arms that gets worse in the sun. The label has nothing on dogs or cats, so call the vet about any new sign you see in your pet after starting it.
The Medication Guide that is part of the label says to store it at room temperature, between 68° and 77°F, and to keep it and all medicines out of the reach of children.
The FDA says the best way to get rid of most unused or expired medicines is a take-back option: a drug take-back location, which can be at a pharmacy or a police station, or a prepaid mail-back envelope. If you cannot use one, the FDA says a medicine that is not on its flush list can go in the trash at home. Its steps are to mix the medicine with something unappealing such as dirt, cat litter or used coffee grounds, without crushing it, and to seal the mixture in a plastic bag before throwing it away. Flushing is only for medicines on that list, such as opioids. Do not give leftovers to another pet.
Write the dose, the times and the stop date here, then print this page for the fridge.
Dose and times: _____________________________________________
Stop date: _____________________________________________