Action heroes like Arnold Schwarzenegger often find themselves faced with an interrogator who uses a truth serum to get the hero to reveal his secrets. In the movies, our heroes are able to resist these potions and hide the truth. Hiding the truth seems to also prepare action heroes for a successful career in politics.

They seem pure fiction, but truth serums do exist. Barbiturates such as sodium amytal and sodium pentothal were first used as truth serums in the early twentieth century. These drugs inhibit control of the central nervous system and were used by physicians to help patients recover forgotten memories or repressed feelings. They are also used for patients with suspected conversion disorder, a condition in which psychological problems produce physical symptoms.

An “amytal interview” is performed by administering a small amount of this drug intravenously. The drug produces a state of drowsiness, slurred speech, and relaxation. This condition makes patients more susceptible to suggestion, allowing the potential to uncover repressed feelings or memories.
Today these interviews are seldom performed. The “truth serum” will not necessarily make you tell the truth. Patients may lose inhibition but will not lose all self-control. Therefore, they are still able to control their behavior and lie. Studies have shown that during these “amytal interviews,” patients often demonstrate a distorted sense of time, show memory disturbances, and have difficulty distinguishing between reality and fantasy, so the line between fact and fiction becomes even more blurred.

-from the book Why Do Men Have Nipples?