Which of the following substances is NOT classified as a CNS depressant?

Benzedrine, which is commonly known by its generic name amphetamine, is not classified as a central nervous system (CNS) depressant because it acts primarily as a stimulant. Stimulants increase brain activity, leading to increased alertness, attention, and energy levels. This is in contrast to CNS depressants, which slow down brain function and can lead to sedation, relaxation, and a decrease in anxiety.

In the context of the other choices, alcohol, Xanax (a benzodiazepine), and Nembutal (a barbiturate) all share the common characteristic of depressing the CNS. These substances can lead to effects such as drowsiness, sedation, and in higher doses, respiratory depression. This fundamental distinction in how Benzedrine functions compared to the other substances makes it clear why it does not belong in the same category as CNS depressants.