A patient with an infectious disease routinely takes their antimicrobial medication with milk or other dairy products in an attempt to reduce stomach upset from the drug. This is most likely to lead to therapeutic failure if the drug is which of the following?
a. Tetracyclines interact with many polyvalent metal cations such that their absorption from the gut (i.e., bioavailability) is reduced. The extent of this reduction can be clinically significant, i.e., leading to inadequate blood levels and effects of the antibiotic.
b. Calcium is, abundant in dairy products. Other metals that can interact with tetracyclines by this mechanism include iron, magnesium, aluminum, and zinc. Note that one or several of these interactants are typically found in antacid products, multivitamin mineral supplements, and even (the trend is growing) in some (mineral-) fortified foods, such as cereals, and citrus juices.
c. Although foods (in general) may interfere with the oral absorption of several other antibiotics, the cation-antibiotic interaction is specific for and important to the tetracyclines.