Which sign is a classic opioid effect?

• A. Seizures
• B. Pinpoint pupils
• C. Diarrhea
• D. Hyperactivity

Answer: (B)

Pinpoint pupils, or miosis, are a classic sign of opioid effects. When opioids activate mu receptors in the brainstem, they enhance parasympathetic outflow to the pupil via the Edinger-Westphal nucleus, causing the pupil to constrict. This constriction is a reliable clue in opioid intoxication or overdose and is frequently observed even when other signs are variable.

Other options don’t fit the typical opioid picture. Seizures can occur with certain opioids at high doses or with drugs like tramadol or meperidine, but seizures are not the hallmark finding. Diarrhea would reflect increased gut motility, whereas opioids generally slow GI transit, leading to constipation rather than diarrhea. Hyperactivity is opposite of the sedating, depressant effects opioids usually produce.