system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does "truth serum" (aka sodium pentathol) work?

Was watching "Arrow" and sodium pentathol was mentioned as a means of exacting truth from an individual. It always seems to be the "go-to" method of getting to the bottom of things in all these action/spy dramas. How exactly does it effect the chemistry of the brain and is it similar to the effects of other drugs (such as alcohol)?
gpt
It doesn't.

Thiopental is from the barbiturate class of drugs, generally they are used as general anesthetics. They bind to a class of brain proteins called GABA to slow down brain activity, and eventually put you to sleep.

What is does is that it significantly slows down higher brain functions and makes it harder for the person to form a coherent lie. But because you are basically interrogating a person who is half asleep, it more likely that he will simply parrot back what you say to him.