Hypergastrinemia, proton pump

The proton pump inhibitors are usually well tolerated however, potential adverse effects include headache, dizziness, somnolence, diarrhea, constipation, and nausea. The frequency of adverse events appears to be similar to that seen with the H2-receptor antagonists. Concern and controversy regarding the safety of therapy with a proton pump inhibitor are based on the proton pump inhibitor s ability to cause hypergastrinemia and gastric carcinoid tumors in rats. After nearly a decade of experience with the proton pump inhibitors, gastric carcinoid tumors have not been directly linked to omeprazole use in humans. ... 

Hypergastrinemia is more frequent and more severe with proton-pump inhibitors than with H2-receptor antagonists, and gastrin levels of >500 ng/L occur in approximately 5 to 10% of users with chronic omeprazole administration. This hypersecretion may predispose patients to rebound hypersecretion of gastric acid upon discontinuation of therapy. 

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