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Omeprazole is the drug representative of the group of proton pump inhibitor drugs (PPI) , used for stomach problems such as heartburn and

We will explain the following aspects regarding omeprazole:

  • Mechanism of action
  • Pharmacokinetics
  • Metabolism
  • Adverse effects
  • Interactions
  • Indications

Mechanism of action

The stomach has an acidic pH due to the HCl produced by the parietal cells of the gastric mucosa. This characteristic acidic pH of the stomach is essential for the digestion of food to achieve:

  • A correct protein denaturation
  • Activate the pepsinogen to peptin so that proteolysis occurs, that is, the breakdown of protein peptide bonds.
  • Prevention of bacterial infections , since bacteria do not usually survive in acidic environments.

With all this, an excessive secretion of gastric acid can cause damage to the mucosa of the gastrointestinal tract, producing ulcers of the stomach and duodenum mainly.


The secretion of gastric acid takes place in several steps:

  1. Segregation of the H⊕ and Cl¯ ions separately in the parietal cells
  2. Its combination to form in HCl in the canaliculi
  3. Segragación of the acid from the canículos to the lumen of the stomach

The , such as omeprazole, act in the final step of acid production, irreversibly binding to the ATPase H⊕ / K¯ pump , being a pH-dependent binding being maximum at pH

This inhibition takes place by the formation of a covalent SS bond between the sulfamide and an accessible cysteine ​​residue of the proton pump, in particular, the omeprazole binds the residue Cys-813 and Ces-892.


Omeprazole, like all other PPIs, is administered in its neutral form, which is inactive . Being a neutral form, it is going to be lipophilic, that is, insoluble in water, and it will be able to easily cross the cell membranes and reach the canaliculi of the parietal cells without problem.

In these cells, as they have acidic pH, they will transform the neutral form of omeprazole to its active protonated form, thus being able to carry out its mechanism of action and irreversibly bind to the proton pump, blocking its action.

  • It is labile in acid medium, so oral preparations are endowed with an enteric coating
  • Its binding to plasma proteins is high , greater than 95%, which increases its possibility of interaction with other drugs, since it may suffer a dose shift.
  • It is absorbed in the small intestine, usually completing at 3-6 h.
  • The oral bioavailability is approximately 35% , being able to increase up to 60% with repeated administration once a day.
  • Its volume of distribution oscillates in 0.3 L / Kg


Omeprazole undergoes hepatic metabolism by the CYP 450 system. Most of its metabolism depends on the specific isoenzyme CYP2C19.

Most of the dose administered orally is excreted as inactive metabolites in the urine and the rest in faeces mainly from biliary secretion.

Adverse effects

It must be borne in mind that omeprazole has a series of adverse effects, although not many due to its selectivity in its action, which must be taken into account if this drug is being administered. Among others we find:

  • In prolonged treatments can produce severe hypomagnesemia
  • Increase the risk of bone fractures
  • Dermal disorders such as rashes or pruritus
  • Gastrointestinal disorders such as diarrhea, constipation, abdominal pain, nausea or vomiting
  • Peripheral neuropathy
  • Hypersensitivity
  • Hemolytic anemia
  • Reduces the absorption of vit B12, which increases the risk of megaloblastic anemia
  • Risk of subacute cutaneous lupus erythematosus
  • Elevates the levels of chromogranin A, a protein that is elevated in certain types of cancer.

Interactions of omeprazole

Omeprazole interacts with many drugs if they are administered simultaneously reducing or potentiating its action.

  • It can reduce the action of:
    • Clopidrogrel
    • Antifungals
    • Phenytoin
    • Rifamycin
    • Mycophenolate
    • Others
  • You can increase the action of:
    • Metrotexate
    • Amphetamines
    • Benzodiazepines
    • Carvedilol
    • Citalopram
    • Escitalopram
    • Ciclosporin
    • Warfarin
    • Others

In short, you can interact with drug numbers, so if you are taking omeprazole with any other medication, you should consult your doctor for the prevention of possible complications.


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