If a medication intended for anxiety causes increased anxiety, what type of effect is this?

The correct answer, which identifies the effect of a medication that causes an increase in anxiety instead of alleviating it, is termed a "paradoxical" effect. Paradoxical reactions are those that produce effects contrary to what is expected based on the medication’s intended purpose or the typical response anticipated in the majority of users. In this situation, an anxiety medication typically aims to reduce anxiety, but if it instead heightens anxiety, it exemplifies this unexpected response.

Understanding this concept is integral for healthcare professionals, as recognizing paradoxical effects can influence treatment decisions and improve patient care. These reactions are particularly relevant in certain populations, such as children or the elderly, who may respond differently to medications.

The other options relate to different pharmacological principles. An idiosyncratic effect is an unusual or abnormal response to a drug that is not predictable and occurs in a small number of patients. The terms "antagonist" and "agonist" refer to drug actions at a receptor level; antagonists block or inhibit a response, while agonists stimulate a response. Neither of these terms would accurately describe the unexpected increase in anxiety caused by the medication.