Which substance is associated with pupillary constriction?

Which substance is associated with pupillary constriction?

• A. Amphetamines
• B. LSD
• C. Heroin
• D. Nicotine

Answer: (C)

Pupillary constriction is a classic sign of opioid effects on the autonomic nervous system. Opioids, like heroin, activate mu receptors in the central nervous system, increasing parasympathetic input to the pupil and causing the iris sphincter to contract. This produces pinpoint (miosis) pupils, especially with intoxication or overdose. In contrast, stimulants such as amphetamines and hallucinogens like LSD boost sympathetic activity, which dilates the pupils (mydriasis). Nicotine can also cause sympathetic stimulation, not typically constriction. Thus, heroin is the substance most consistently associated with pupillary constriction.

Pupillary constriction is a classic sign of opioid effects on the autonomic nervous system. Opioids, like heroin, activate mu receptors in the central nervous system, increasing parasympathetic input to the pupil and causing the iris sphincter to contract. This produces pinpoint (miosis) pupils, especially with intoxication or overdose.

In contrast, stimulants such as amphetamines and hallucinogens like LSD boost sympathetic activity, which dilates the pupils (mydriasis). Nicotine can also cause sympathetic stimulation, not typically constriction. Thus, heroin is the substance most consistently associated with pupillary constriction.