True about proton-pump inhibitor omeprazole is
**Core Concept**
Proton-pump inhibitors (PPIs) like omeprazole work by irreversibly inhibiting the H+/K+ ATPase enzyme in the parietal cells of the stomach, reducing gastric acid secretion.
**Why the Correct Answer is Right**
Omeprazole is a prodrug that is metabolized by CYP2C19 to its active form, omeprazole sulfenate. This active form covalently binds to the H+/K+ ATPase enzyme, irreversibly inhibiting its activity and reducing gastric acid secretion. The resulting decrease in gastric pH helps alleviate symptoms of gastroesophageal reflux disease (GERD), peptic ulcers, and other acid-related disorders.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it does not specify the mechanism of action of omeprazole. While PPIs do reduce gastric acid secretion, this option is too vague and does not accurately describe the enzyme inhibition.
**Option B:** Incorrect because it implies that omeprazole works on the stomach lining, which is not accurate. Omeprazole's mechanism of action is at the level of the parietal cells and the H+/K+ ATPase enzyme.
**Option C:** Incorrect because it suggests that omeprazole is a direct-acting acid inhibitor, which is not the case. Omeprazole requires metabolic activation to exert its effect.
**Clinical Pearl / High-Yield Fact**
Omeprazole and other PPIs can increase the risk of Clostridioides difficile infection due to the alteration of the gut microbiome, particularly in hospitalized patients.
**Correct Answer:** C.