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Omeprazole

Prilosec | Losec | Omesec

FDA ApprovedGastrointestinal AgentsProton Pump Inhibitors
FDA: 1989Half-life: 0.5-1 hour (plasma); antisecretory effect lasts 72+ hoursPregnancy: Category C

Overview

Irreversibly blocks the hydrogen/potassium adenosine triphosphatase enzyme system (H+/K+ ATPase or gastric proton pump) of the gastric parietal cell, suppressing gastric acid secretion.

Indications

  • Gastroesophageal reflux disease (GERD)
  • Peptic ulcer disease
  • Zollinger-Ellison syndrome
  • H. pylori eradication (combination therapy)
  • NSAID-induced ulcer prevention

Contraindications

  • Hypersensitivity to omeprazole or substituted benzimidazoles
  • Concurrent use with rilpivirine-containing products

Classification

Gastrointestinal AgentsProton Pump InhibitorsGastrointestinal Tract

Mechanism of Action

Irreversibly blocks the hydrogen/potassium adenosine triphosphatase enzyme system (H+/K+ ATPase or gastric proton pump) of the gastric parietal cell, suppressing gastric acid secretion.

Pharmacodynamics

Suppresses gastric acid secretion by specific inhibition of the proton pump in parietal cells. Effects are dose-related and lead to inhibition of both basal and stimulated acid secretion.

Pharmacokinetics

Absorption
Rapid absorption; bioavailability increases with repeated dosing. Delayed-release formulation with enteric coating.
Distribution
Protein binding 95%. Volume of distribution 0.3 L/kg.
Metabolism
Hepatic via CYP2C19 (major) and CYP3A4 (minor). Polymorphic metabolism.
Excretion
Renal (77%) and fecal (18-23%).
Half-life
0.5-1 hour (plasma); antisecretory effect lasts 72+ hours
Bioavailability
30-40% (single dose), up to 60% (repeated doses)
Protein Binding
95%

Dosage

Typical dosage: 20-40mg once daily before meals

Available Forms

  • Capsule (delayed-release)
  • Tablet
  • Powder for oral suspension
  • IV injection

Side Effects

Common

  • Headache
  • Abdominal pain
  • Nausea
  • Diarrhea
  • Flatulence

Serious

  • C. difficile-associated diarrhea
  • Bone fractures (long-term)
  • Hypomagnesemia
  • Vitamin B12 deficiency

Rare

  • Interstitial nephritis
  • Cutaneous lupus erythematosus
  • Fundic gland polyps

Drug Interactions

major

Omeprazole inhibits CYP2C19, reducing conversion of clopidogrel to its active metabolite and decreasing antiplatelet effect.

moderate

PPIs may increase methotrexate levels by inhibiting renal elimination, particularly at high doses.

Warnings

Pregnancy

Category C

Toxicity

LD50 >4000 mg/kg (oral, rat)

Overdose

Symptoms: confusion, drowsiness, blurred vision, tachycardia. Treatment: supportive care, not significantly removed by dialysis.

References

Looking for patient-friendly information? Visit RemedyDoor for easy-to-read guides about this medication.