Which substance is categorized as a CNS depressant?

Barbiturates are categorized as central nervous system (CNS) depressants because they work by enhancing the effects of the neurotransmitter gamma-aminobutyric acid (GABA) in the brain. This results in sedation, muscle relaxation, and a decrease in anxiety. They are frequently used to treat anxiety and sleep disorders, but their potential for addiction and overdose is significant, and they can slow down brain activity, heart rate, and respiratory function.

In contrast, caffeine is a CNS stimulant that promotes alertness and can increase heart rate. Nicotine, primarily known as a stimulant found in tobacco products, can have a complex effect as it initially stimulates the CNS but can also lead to depressive effects after prolonged use. Acetaminophen is an analgesic and antipyretic medication, not classified as a CNS depressant, and operates differently by inhibiting certain chemicals in the brain that signal pain and fever.