Ironically, the formulation of dragonbane originated from the same creature it was intended to harm. It was composed of the blood of three different varieties of dragons.
Dragonbane appeared as an opaque, bright-blue liquid.
When any non-dragon creature was exposed to dragonbane, they felt extreme pain throughout their body, including their internal organs.
When a dragon was affected by the poison, by mere contact alone, they became unable to breath for a period of time.
Flagrant imitations of this potent poison were more often encountered in the Realms than the genuine substance. This was partially due to the fact that dragons regularly killed-on-sight any individual they encountered who carried true dragonbane.