Fast-Penta was a drug widely used in the Nexus for its "truth serum" properties. Use of this drug outside of criminal investigations appeared to be generally illegal, but on some planets people signed waivers to permit its use by their employers. Some people were allergic to the drug, either naturally or through one of six known induced reactions. A normal response to the drug included improved memory, very literal thinking, and a compulsion to tell the full truth. Further responses to the drug varied widely, but included euphoria, laughter, drooling, weeping, and/or simple relaxation.