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.

Other medical uses for fast-penta included memory recovery in persons with amnesia. Other medical drugs with fast-penta-like properties included Clarium and IV Thalizine-5.

Certain people, such as Cetagandan ba and haut, were resistant or even immune to fast penta.


Most books in the Vorkosigan Saga mention the drug. Interesting references include:

  • Falling Free, chapter 4 (IV Thalizine-5, and mention of restrictions in its use)
  • Cetaganda, chapter 14 (Clarium and its lack of effectiveness on Haut)
  • Diplomatic Immunity, chapters 12 and 17 (six anaphylaxes and its lack of effectiveness on Ba)
  • Mirror Dance, chapter 22 (medical use to recover memories)

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