Don't do it!

CS extract is almost entirely water and it is not generally a good idea to inject much water - even pharmaceutical grade water made for reconstituting injectibles which have been freeze-dried or otherwise condensed.

Washing is fine, swishing in the mouth is fine, and taking internally is fine.  I would not even think about injecting anything that was not specifically made for injecting without doing so under the supervision of a qualified professional.

DQ