Omeprazole Therapy Causes Malabsorption of Cyanocobalamin (Vitamin B12)

Omeprazole Therapy Causes Malabsorption of Cyanocobalamin (Vitamin B₁₂)

From East Carolina University School of Medicine, Greenville, North Carolina. Request for Reprints: Stefan P. Marcuard, MD, Section of Gastroenterology, Department of Medicine, East Carolina University School of Medicine, Greenville, NC 287858-4354. Acknowledgments: The authors thank the Human Health Division of Merck, Inc. for its support; and the Department of Medicines, Text/Information Processing Center for preparation of the manuscript. Grant Support: In part by grant 585451 from the American College of Gastroenterology.

Abstract

Objective: To evaluate protein-bound cyanocobalamin (vitamin B₁₂) sub absorption before and after omeprazole (Prilosec) therapy in healthy male volunteers.

Design: Clinical trial in which each volunteer served as his own control.

Setting: Outpatient department of a university medical center.

Participants: Ten healthy, male volunteers 22 to 50 years old.

Intervention: Each participant had a modified Schilling test (protein-bound cyanocobalamin) and a gastric analysis, as well as measurements of serum vitamin B₁₂, gastrin, and folate levels. Five patients were then randomly assigned to take either 20 mg or 40 mg of omeprazole daily. After 2 weeks of omeprazole therapy, these tests were repeated.

Measurements: The modified Schilling test, gastric analysis, serum gastrin level, folate level, and cyanocobalamin level.

Results: At the end of the 2-week treatment period, cyanocobalamin absorption decreased from 3.2% to 0.9% (P = 0.031) in participants receiving 20 mg of omeprazole daily. In patients taking 40 mg of omeprazole daily, cyanocobalamin absorption decreased from 3.4% to 0.4% (P < 0.05).

Conclusions: Omeprazole therapy acutely decreased cyanocobalamin absorption in a dose-dependent manner.