Tetracycline may accumulate in bone because of which interaction?

• A. Complex formation with Calcium
• B. Binding to albumin
• C. Metabolism by liver
• D. Active transport into bone

Answer: (A)

This question centers on how tetracycline interacts with mineralizing tissue. Tetracycline can chelate calcium ions, forming a calcium-tetracycline complex. In bone, where calcium is abundant in the hydroxyapatite matrix, the drug binds to calcium and becomes incorporated into the mineralizing tissue, leading to accumulation. The other options don’t explain this deposition: binding to albumin affects blood distribution but doesn’t drive bone deposition; liver metabolism alters or clears the drug rather than trapping it in bone; active transport into bone would require a transport mechanism that isn’t the primary reason for this accumulation. So, complex formation with calcium best accounts for tetracycline’s buildup in bone.