In the 1950s, American scientists began searching for a drug which when given to a person would compel him to speak the truth, regardless of the consequences.
There were reports that the Koreans and Chinese were using such a drug to get information from American soldiers captured in the Korean war.
The scientists experimented with all sorts of drugs including amphetamines (pep pills), barbiturates (sleeping pills), cocaine and alcohol, but to no avail. They could not find a drug that would make a person tell the truth if he didn't want to.
Nevertheless in the late 1950s a drug called Thiopentone sodium gained a reputation as a 'truth serum'. Thiopentone sodium is used in hospitals to put people to sleep before an operation. In smaller doses it relaxes a person and helps him to talk more freely than he normally would.
The secret police of some countries began to use Thiopentone sodium along with hypnosis while questioning political prisoners. The person was made unconscious with an injection of the drug and then partially revived and subjected to hypnosis. The hypnotist would make the person feel he was among friends and people he could trust, and the prisoner would then speak freely, and often truthfully.
Thiopentone sodium is now sometimes used in psychiatric treatment.