Pupil dilation is most likely associated with which of the following substances?

Pupil dilation is most likely associated with which of the following substances?

• A. Opiates
• B. Cocaine
• C. Methamphetamine
• D. Ketamine

Answer: (B)

Pupil size reflects the balance between sympathetic and parasympathetic activity. Sympathetic activation widens the pupil (mydriasis) by stimulating the iris dilator muscle, while parasympathetic activity constricts it. Cocaine is a classic stimulant that increases levels of norepinephrine in the synapse by blocking its reuptake. This boosts sympathetic tone, producing effects such as tachycardia, hypertension, sweating, and notably, pupil dilation. Opiates, in contrast, tend to cause pinpoint pupils because they enhance parasympathetic influence, not dilation. Methamphetamine can also cause dilation due to increased monoamines, and ketamine may cause some mydriasis, but cocaine is the most prototypical example of a substance associated with dilated pupils.

Pupil size reflects the balance between sympathetic and parasympathetic activity. Sympathetic activation widens the pupil (mydriasis) by stimulating the iris dilator muscle, while parasympathetic activity constricts it.

Cocaine is a classic stimulant that increases levels of norepinephrine in the synapse by blocking its reuptake. This boosts sympathetic tone, producing effects such as tachycardia, hypertension, sweating, and notably, pupil dilation. Opiates, in contrast, tend to cause pinpoint pupils because they enhance parasympathetic influence, not dilation. Methamphetamine can also cause dilation due to increased monoamines, and ketamine may cause some mydriasis, but cocaine is the most prototypical example of a substance associated with dilated pupils.