Effect of milk on effectiveness of oral tetracycline?

Question

Tetracycline is known to be inhibited by calcium ions, and milk contains quite some calcium ions. What I want to ask is, to what extent does drinking milk affect the effectiveness of orally taken tetracycline?

Answer 1

Milk contains calcium, an ion, that when in the presence of the antibiotic class Tetracyclines will bind to them and deem them ineffective. This is because the gut will no longer be able to absorb them. Both calcium and aluminum will prevent the tetracyclines from being absorbed. The extent of this interference of absorption will be anywhere from 50-90%.