Rosh Psychiatry Board Practice Exam

In a patient with altered mental status and respiratory depression, what finding would likely indicate opioid intoxication?

1. Elevated temperature

2. Miosis

3. Mydriasis

4. Tremor

The correct answer is: Miosis

In a patient presenting with altered mental status and respiratory depression, miosis, or pinpoint pupils, is a classic sign of opioid intoxication. Opioids exert their effects by binding to specific receptors in the brain, leading to a range of symptoms. One of these effects is the stimulation of the Edinger-Westphal nucleus within the cranial nerve III, which results in pupil constriction. While other symptoms may be present in cases of opioid intoxication, such as sedation or respiratory depression, the presence of miosis is a key distinguishing feature. This can help differentiate opioid use from other types of substance intoxication, which may present with different pupil sizes. For instance, mydriasis, characterized by dilated pupils, is often associated with sympathomimetics or hallucinogenic substances, while elevated temperature and tremors may suggest other conditions related to withdrawal or different intoxications entirely. Thus, the presence of pinpoint pupils strongly supports a diagnosis of opioid intoxication in the clinical scenario described.