The nurse is educating a client about taking a tetracycline along with an antacid. The nurse explains to the client not to take these two medications because the antacid can reduce the absorption of the tetracycline. When one drug reduces the effect of another, it is:

A. An allergic reaction: An allergic reaction is an immune response, not the reduction of drug effect. B. A synergistic effect: A synergistic effect occurs when two drugs enhance each other's effects. C. An antagonistic effect: An antagonistic effect occurs when one drug reduces or counteracts the effect of another drug. D. None of the above: The correct term is "antagonistic effect."