A simple "extraction". Assuming it's an acid salt, it should be water soluble, so rinse with water a few times, collect all the water. Then evaporate the water in question on a hot plate and there you have some fresh powder to collect and burn. But then again, I'm unfamiliar with said drugs, so I'm going off general chemistry knowledge. If it happens to be a freebase, ethanol should do the trick (or if you feel exotic, diethyl ether or chloroform); said solvents also allow faster and easier evaporation - use caution with chloroform as it is hepatotoxic among other things.
Assuming that the quantity is fairly small, you may want to use a smaller surface for evaporation and smaller amounts of a solvent. Then again this makes me question the need for the whole ordeal, is it really worth the trouble?