What term describes a drug that prevents the action of another drug or chemical?

The term that describes a drug that prevents the action of another drug or chemical is "antagonist." An antagonist works by binding to a receptor without activating it, thereby blocking or diminishing the effect of another substance (often an agonist). This mechanism is essential in pharmacology because it allows for modulation of physiological responses in the body, especially in the treatment of various medical conditions.

For example, in the context of opioid medications and their potential for misuse, an opioid antagonist like naloxone is utilized to counteract the effects of opioid overdose. It does this by displacing the opioid from the receptor sites in the brain, reversing the potentially life-threatening effects caused by excessive opioid activity.

In contrast, an agonist refers to a substance that activates a receptor to produce a biological response. A catalyst is a substance that increases the rate of a chemical reaction without being consumed in the process. A synergist is a term used to describe substances that enhance each other's effects when administered together, rather than one preventing the action of the other. Understanding these distinctions is crucial for medical professionals when considering drug interactions and therapeutic strategies.