While fictional accounts of intelligence interrogation gives these drugs near magical abilities, information obtained by publicly-disclosed truth drugs has been shown to be highly unreliable, with subjects apparently freely mixing fact and fantasy. Much of the claimed effect relies on the belief of the subject that they cannot tell a lie while under the influence of the drug.

From what I can tell, the last use of sodium thiopental (pentathol in laymen's terms) as a truth serum was during the KGB. It was revived to interrogate the "terrorists" of 9/11, but failed. Horribly.