National Certified Addiction Counselor, Level 2 (NCAC II) Practice Exam 2025 – All-in-One Guide to Exam Success!

Question: 1 / 760

What is an example of a substance that causes miosis?

Cocaine

Amphetamines

Heroin

Miosis, or constricted pupils, is commonly associated with certain substances. Heroin, an opioid, is well-known for causing miosis. This effect occurs because opioids, including heroin, activate specific receptors in the brain that lead to a decrease in the activity of the muscles controlling the size of the pupils. Therefore, when a person uses heroin, it often results in pinpoint pupils, a classic sign of opioid use.

In contrast, other substances mentioned in the options, like cocaine and amphetamines, typically lead to mydriasis, or dilated pupils, due to their stimulant effects and interaction with neurotransmitters such as norepinephrine. Atropine, an anticholinergic agent, also causes pupil dilation by blocking the action of the neurotransmitter acetylcholine. This makes heroin the most fitting answer when identifying a substance that causes miosis.

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Atropine

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