Answers: http://mb.rxlist.com/rxboard/tetracyclin...
Quote:
Tetracyclines should not be taken with dairy products, antacids, laxatives, or iron supplements. If you require these medication, you cannot take them inwardly 2 hours of your Tetracycline dose. The reason is because these medication contain metal ions that bind to the tetracycline. This is called chelation, which method it inactivates the tetracycline which causes it not to be capable of work. --cs
Hope that helps.
Dairy products, antacids, and some multi-vitamins will lower the usefulness of some antibiotics and other pills. Usually, you are just not supposed to hold dairy within two hours of taking them so they can hold your attention properly.