Question

Which of the following drugs causes Vitamin B12 deficiency on long-term use?

• A. Metformin
• B. Omeprazole
• C. Colchicine
• D. All of the above

Hint:

Multiple drugs impair B12 absorption through different mechanisms involving gastric acid, ileal transport, or mucosal function.

Answer 1

The Correct Option is D

Step 1: Understand mechanisms of drug-induced B12 deficiency.
Vitamin B12 (cobalamin) absorption requires intrinsic factor (IF) secreted by gastric parietal cells and an alkaline environment in the terminal ileum.

Step 2: Metformin.
Metformin inhibits calcium-dependent absorption of the IF-B12 complex in the terminal ileum. This occurs in approximately 5-10% of long-term users and is dose-dependent. It is reversible with calcium supplementation.

Step 3: Omeprazole (Proton Pump Inhibitors).
PPIs suppress gastric acid secretion, which impairs the release of protein-bound B12 from food (requires acid and pepsin). Long-term PPI use is an established cause of B12 deficiency, particularly in the elderly.

Step 4: Colchicine.
Colchicine inhibits absorption of the IF-B12 complex in the terminal ileum by disrupting ileal mucosal cell function. It is a less commonly tested but well-documented cause.

Step 5: Conclusion.
All three drugs -- metformin, omeprazole, and colchicine -- can cause Vitamin B12 deficiency through different mechanisms. Other drugs include H2 blockers, neomycin, and para-aminosalicylic acid (PAS).

Answer: All of the above