Voraxna

From Memory Alpha, the free Star Trek reference

Voraxna is a type of poison effective against Cardassians.

In 2373, Dukat had voraxna added to a bottle of kanar, which was then delivered to Tekeny Ghemor.

Benjamin Sisko later confronted Dukat and Weyoun with the poisoned kanar, which according to him was enough to kill a dozen Cardassians. Weyoun drank the kanar and the poison, saying it was "quite toxic". (DS9: "Ties of Blood and Water")