Omeprazole is a proton pump inhibitor (PPI). It requires acid activation to become the active sulfenamide. The consequence of this for drug administration is:

• A Omeprazole must be taken with food to trigger gastric acid secretion that activates the drug
• B Omeprazole is activated in the bloodstream by plasma esterases before reaching parietal cells
• C Omeprazole requires alkaline pH for activation and should be taken after meals when gastric pH rises
• D Omeprazole must be enteric-coated (acid-resistant) and taken before meals; it is activated by parietal cell canalicular acid (pH <4) and forms a covalent disulfide bond with cysteine-813 of the H+/K+-ATPase ✓

Explanation

Omeprazole is a substituted benzimidazole that is unstable in acid at the stomach lumen and requires enteric coating for oral administration; once absorbed and accumulated in the acidic secretory canaliculi of active parietal cells (pH ~1–2), it is protonated and rearranges to a sulfenamide/sulfenic acid that covalently bonds to cysteines on the luminal face of H+/K+-ATPase (primarily Cys-813 and Cys-892), irreversibly blocking the enzyme. Taking PPIs 30–60 minutes before a meal maximizes the number of active pumps for irreversible inhibition.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.