Omeprazole is useful in gastric and duodenal ulcer disease. It also shows efficiacy against gastric erosions caused by ulcer prone drugs such as NSAIDs.
In the stomach omeprazole is activated to a form that binds irreversibly at the surface of parietal cells to the enzym H/K ATPase. It thereby inhibits the transport of hydrogen ions into the stomach. The net effects is that omeprazole reduces acide secretion during both basal and stimulated conditions.
OMP is rapidly absorbed from the gut; the human commercial product is an enteric coated granule form as the drug is rapidly degraded by acid. The commercial oral pastes consist of some enteric coated options and some uncoated options.
OMP is extensively metabolised in the liver to at least six different metabolites. These are excreted principally in the urine.
OMP in dogs has an average serum half life of about 1 one hour, however, due to the nature of its effects as an irreversible inhibitor the therapeutic effect may last between 24-72 hours.
OMP is contraindicated in hypersensitive cases.
Care should be exercised in patients who have hepatic and/or renal disease
When used at therapeutic doses adverse reactions are rare. However, hypersensitivity reactions theoretically may occur at any dose level. The most common adverse effects are listed below:
- GI distress (anorexia, colic, nausea, vomiting, flatulence, diarrhoea)
- hematologic abnormalities
- urinary tract infections, proteinuria, or CNS disturbances.
- chronic high doses can cause enterochromaffin-like cell hyperplasia
- gastric carcinoid tumours
DRUG INTERACTIONS The following drug interactions have either been reported or theoretical:
- Drugs requiring decreased gastric pH for optimal absorption
- 4mg/kg twice daily for 5 days for treatment of gastric ulcer
- 2mg/kg daily for prevention