Promazine

From Memory Alpha, the free Star Trek reference

Promazine was a clear round pill developed by the Obsidian Order for use by their operatives in case of capture. The pill not only kills a person but turns them into dust within hours, leaving nothing left for identification.

Dukat tried to use promazine to kill his followers on Empok Nor in 2375. (DS9: "Covenant")

[edit] External link

Promazine at Wikipedia