Which of the following is not typically categorized as a stimulant?

• A. Amphetamine
• B. Methamphetamine
• C. Cocaine
• D. Heroin

Answer: (D)

Stimulants raise central nervous system activity and bodily arousal, boosting energy, alertness, and focus. Amphetamine and methamphetamine do this by increasing dopamine and norepinephrine in the brain, which gives you more wakefulness and energy. Cocaine also heightens arousal by blocking the reuptake of dopamine, norepinephrine, and serotonin, leading to a burst of energy and heightened alertness.

Heroin, by contrast, is an opioid. It acts on mu-opioid receptors to produce analgesia, relaxation, euphoria, and slowed breathing rather than increased arousal. This depressant effect on the CNS means heroin is not categorized as a stimulant, even though it influences brain reward pathways in different ways.