A medication used to improve the symptoms of heartburn, and to treat related conditions such as ulcers, tissue damage and infection with the bacteria called H. pylori.


A proton pump inhibitor used to treat GERD associated conditions such as heartburn and gastric acid hypersecretion, and to promote healing of tissue damage and ulcers caused by gastric acid and H. pylori infection.


Originally approved by the FDA in 1989, omeprazole is a _proton-pump inhibitor_, used to treat gastric acid-related disorders. These disorders may include gastroesophageal reflux disease (GERD), peptic ulcer disease, and other diseases characterized by the oversecretion of gastric acid. This drug was the first clinical useful drug in its class, and its approval was followed by the formulation of many other proton pump inhibitor drugs [6]. Omeprazole is generally effective and well-tolerated, promoting its popular use in children and adults [FDA label].



Omeprazole, according to the FDA label [FDA label] is a proton pump inhibitor (PPI) used for the following purposes:

• Treatment of active duodenal ulcer in adults

• Eradication of Helicobacter pylori to reduce the risk of duodenal ulcer
recurrence in adults

• Treatment of active benign... Read more


**Effects on gastric acid secretion**

This drug decreases gastric acid secretion [FDA label]. After oral administration, the onset of the antisecretory effect of omeprazole is usually achieved within one hour, with the maximum effect occurring by 2 hours after administration. The inhibitory effec... Read more

Mechanism of action

Hydrochloric acid (HCl) secretion into the gastric lumen is a process regulated mainly by the H(+)/K(+)-ATPase of the proton pump [ Read more


Omeprazole delayed-release capsules contain an enteric-coated granule formulation of omeprazole (because omeprazole is acid-labile), so that absorption of omeprazole begins only after the granules exit the stomach [FDA label].

Absorption of omeprazole occurs rapidly, with peak plasma concentrati... Read more

Protein binding

Approximately 95% bound to human plasma proteins [FDA label].

Volume of distribution

Approximately 0.3 L/kg, corresponding to the volume of extracellular water [5].


Healthy subject (delayed release capsule), total body clearance 500 - 600 mL/min [FDA label]Geriatric plasma clearance: 250 mL/min [FDA label]Hepatic impairment plasma clearance: 70 mL/min [FDA label]

Half life

0.5-1 hour (healthy subjects, delayed-release capsule) [FDA label]
Approximately 3 hours (hepatic impairment) [FDA label]

Route of elimination

After a single dose oral dose of a buffered solution of omeprazole, negligible (if any) amounts of unchanged drug were excreted in urine. Most of the dose (about 77%) was eliminated in urine as at least six different metabolites. Two metabolites were identified as _hydroxyomeprazole_ and the corresp... Read more


**Oral acute (LD50)**: 4000 mg/kg (mouse), 2210 mg/kg (rat) [MSDS].


Symptoms of overdose include confusion, drowsiness, blurred vision, tachycardia, nausea, diaphoresis, flushing, headache, and dry mouth.

**Carcinogenesis and mutagenesis**

In 24-month studies in rats, a dos... Read more

Adverse Effects


  • Route:
    • Oral
  • Hypersensitivity:
    • true
    • Substituted benzimidazoles
  • Regions: US
  • Route:
    • Oral
  • Hypersensitivity:
    • true
  • Regions: US

Food Interactions

  • Take before a meal. Allow 30-60 minutes before a meal.


Type in a drug name to check for interaction with Omeprazole
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  • Paracetamol(acetaminophen)
  • Paxil(paroxetine)
  • Pamelor(nortriptyline)
  • Panadol(acetaminophen)
  • Patanol(olopatadine ophthalmic)
  • Pataday(olopatadine ophthalmic)
  • Parnate(tranylcypromine)
  • Pazeo(olopatadine ophthalmic)
The metabolism of (R)-warfarin can be increased when combined with Omeprazole.
The metabolism of (S)-Warfarin can be increased when combined with Omeprazole.
The metabolism of 4-hydroxycoumarin can be increased when combined with Omeprazole.
The metabolism of 4-Methoxyamphetamine can be decreased when combined with Omeprazole.
The metabolism of 5-methoxy-N,N-dimethyltryptamine can be decreased when combined with Omeprazole.
The metabolism of 6-O-benzylguanine can be increased when combined with Omeprazole.
The metabolism of 8-azaguanine can be increased when combined with Omeprazole.
The metabolism of 8-chlorotheophylline can be increased when combined with Omeprazole.
The metabolism of 9-aminocamptothecin can be increased when combined with Omeprazole.
The metabolism of 9-Deazaguanine can be increased when combined with Omeprazole.
The metabolism of 9-Methylguanine can be increased when combined with Omeprazole.
The metabolism of Omeprazole can be increased when combined with Abatacept.
Omeprazole may decrease the excretion rate of Abemaciclib which could result in a higher serum level.
The metabolism of Omeprazole can be increased when combined with Abiraterone.
The metabolism of Acalabrutinib can be increased when combined with Omeprazole.
The metabolism of Acebutolol can be decreased when combined with Omeprazole.
The metabolism of Acefylline can be increased when combined with Omeprazole.
The metabolism of Acenocoumarol can be increased when combined with Omeprazole.
The metabolism of Acetaminophen can be increased when combined with Omeprazole.
The metabolism of Acetohexamide can be decreased when combined with Omeprazole.
18 References
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  2. 2 . Castell D: Review of immediate-release omeprazole for the treatment of gastric acid-related disorders. Expert Opin Pharmacother. 2005 Nov;6(14):2501-10. doi: 10.1517/14656566.6.14.2501 .PubMed: 16259581
  3. 3 . Higuera-de-la-Tijera F: Efficacy of omeprazole/sodium bicarbonate treatment in gastroesophageal reflux disease: a systematic review. Medwave. 2018 Mar 14;18(2):e7179. doi: 10.5867/medwave.2018.02.7179.PubMed: 29547594
  4. 4 . Welage LS, Berardi RR: Evaluation of omeprazole, lansoprazole, pantoprazole, and rabeprazole in the treatment of acid-related diseases. J Am Pharm Assoc (Wash). 2000 Jan-Feb;40(1):52-62; quiz 121-3.PubMed: 10665250
  5. 5 . Cederberg C, Andersson T, Skanberg I: Omeprazole: pharmacokinetics and metabolism in man. Scand J Gastroenterol Suppl. 1989;166:33-40; discussion 41-2.PubMed: 2690330
  6. 6 . Strand DS, Kim D, Peura DA: 25 Years of Proton Pump Inhibitors: A Comprehensive Review. Gut Liver. 2017 Jan 15;11(1):27-37. doi: 10.5009/gnl15502.PubMed: 27840364
  7. 7 . McTavish D, Buckley MM, Heel RC: Omeprazole. An updated review of its pharmacology and therapeutic use in acid-related disorders. Drugs. 1991 Jul;42(1):138-70. doi: 10.2165/00003495-199142010-00008.PubMed: 1718683
  8. 8 . Langtry HD, Wilde MI: Omeprazole. A review of its use in Helicobacter pylori infection, gastro-oesophageal reflux disease and peptic ulcers induced by nonsteroidal anti-inflammatory drugs. Drugs. 1998 Sep;56(3):447-86. doi: 10.2165/00003495-199856030-00012.PubMed: 9777317
  9. 9 . Lewin MJ: Cellular mechanisms and inhibitors of gastric acid secretion. Drugs Today (Barc). 1999 Oct;35(10):743-52.PubMed: 12973369
  10. 10 . Sachs G, Wallmark B: The gastric H+,K+-ATPase: the site of action of omeprazole. Scand J Gastroenterol Suppl. 1989;166:3-11.PubMed: 2557669
  11. 11 . Sachs G, Shin JM, Howden CW: Review article: the clinical pharmacology of proton pump inhibitors. Aliment Pharmacol Ther. 2006 Jun;23 Suppl 2:2-8. doi: 10.1111/j.1365-2036.2006.02943.x.PubMed: 16700898
  12. 12 . Sung JJ, Kuipers EJ, El-Serag HB: Systematic review: the global incidence and prevalence of peptic ulcer disease. Aliment Pharmacol Ther. 2009 May 1;29(9):938-46. doi: 10.1111/j.1365-2036.2009.03960.x.PubMed: 19220208
  13. 13 . Vcev A, Stimac D, Vceva A, Takac B, Pezerovic D, Ivandic A: High dose omeprazole plus amoxicillin and azithromycin in eradication of Helicobacter pylori in duodenal ulcers. Helicobacter. 1999 Mar;4(1):54-7.PubMed: 10352088
  14. 14 . Scott DR, Sachs G, Marcus EA: The role of acid inhibition in Helicobacter pylori eradication. F1000Res. 2016 Jul 19;5. doi: 10.12688/f1000research.8598.1. eCollection 2016.PubMed: 30023042
  15. 15 . Mobley HL: The role of Helicobacter pylori urease in the pathogenesis of gastritis and peptic ulceration. Aliment Pharmacol Ther. 1996 Apr;10 Suppl 1:57-64.PubMed: 8730260
  16. 16 . FDA Approved Drug Products: Talicia Amoxicillin, Omeprazole, and Rifabutin Oral Delayed Release Capsules Link
  17. 17 . NIH StatPearls: Omeprazole Link
  18. 18 . FDA Approved Products: Prilosec (omeprazole) delayed release capsules Link