Which of the following is a classic sign of opioid withdrawal?

Mydriasis, or dilation of the pupils, is indeed a classic sign of opioid withdrawal. Opioids typically cause miosis, which is constriction of the pupils, when a person is actively using these substances. Conversely, during withdrawal, the body reacts to the absence of opioids by reversing this effect, leading to mydriasis. This physiological change is part of the body's readjustment process as it attempts to regain homeostasis after the cessation of opioid use.

In contrast, signs such as bradycardia and hypotension are often associated with opioid use rather than withdrawal. Opioids can depress the central nervous system, leading to a slowing heart rate and lower blood pressure while intoxicated. Additionally, while decreased appetite can occur during withdrawal, it is not as prominently recognized as a classic sign compared to mydriasis. Therefore, mydriasis stands out as a key indicator of opioid withdrawal, illustrating the body's response as it attempts to compensate for the lack of opioids affecting the nervous system.