Omeprazole
Class: ulcer healing/prophylactic – proton pump inhibitor
Indications (NB some may be unlicensed): duodenal/gastric ulcer, reflux oesophagitis, dyspepsia, NSAID associated gastric and duodenal ulcer/erosion treatment
Contraindications/cautions: renal impairment; no more than 20 mg daily in hepatic impairment
Adverse reactions: common: headache, nausea/vomiting, diarrhoea or constipation; less common: insomnia, dizziness, vertigo, pruritus, blood disorders, muscle/joint pain, dry mouth, agitation
Metabolism/clearance: metabolised by metabolising enzyme CYP2C19 mainly in the liver
Interactions:
- increased clinical effect/toxicity of omeprazole (due to increased blood concentrations) may occur with some CYP metabolising enzyme inhibitors (see above) e.g. fluconazole, fluoxetine, ketoconazole
- decreased clinical effect/toxicity of omeprazole (due to decreased blood concentrations) may occur with some CYP metabolism enzyme inducers (see above) e.g. carbamazepine, phenytoin, rifampicin
- increased clinical effect/toxicity of some drugs (due to increased blood concentrations of them) may occur with omeprazole due to metabolising enzyme inhibition by omeprazole e.g. diazepam
- decreased absorption of itraconazole may occur with omeprazole
| Dosing: | |
|---|---|
| oral: | 10 to 40 mg once a day |
| subcut: | injection and infusion available but not usually used subcut. Doses of 40 mg in 100 mL normal saline have been given subcut over 3 hours |
| rectal: | not available |
Syringe driver: short infusions only
Mechanism of action: inhibits gastric acid secretion via proton pump blockade
Onset: oral (antacid effect): 10 to 20 minutes
Notes:
- omeprazole is considered the drug of choice for prophylaxis or treatment of NSAID-induced gastro-intestinal damage
- oral suspension can be made