Which agent is described as reducing antibiotic absorption?

• A. Calcium & Magnesium
• B. Vitamin C
• C. Antibiotics
• D. Vitamin E

Answer: (C)

Drug-nutrient interactions can affect how well an antibiotic is absorbed in the gut. Minerals like calcium and magnesium can bind to certain antibiotics (such as tetracyclines and fluoroquinolones) and form insoluble chelate complexes. These complexes stay in the intestinal tract and are not absorbed, so the antibiotic’s bioavailability drops.

That’s why it’s advised to time administration so the antibiotic is taken at a distance from calcium- or magnesium-containing products, dairy, or antacids—typically a couple of hours before or after. Other agents like vitamin C or vitamin E don’t have this same chelation effect with these antibiotics, so they’re not the cause of reduced absorption in this context.