Sodium pentothal -- the original " truth serum" -- was discovered in 1936 by Ernest H.

CNN: 'Truth serum' won't reveal mind of James Holmes

Sodium pentothal, the trade name for thiopental, is the best-known of a class of barbiturates popularly supposed to act as truth serums.

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Sodium pentothal is still used today to knock out patients before they are given another, longer-lasting anesthetic to keep them unconscious during surgery.

CNN: 'Truth serum' won't reveal mind of James Holmes

Sodium pentothal made surgery far less painful.

CNN: 'Truth serum' won't reveal mind of James Holmes