i was trying liquid suppositories at one time, especially for b-12, and i used a syringe like they give you to give babies liquid medicine. i found it to be a great to administer substances into the body and bypass the gauntlet of the gut. it works somewhere in between injection and transdermal/sublingual. in fact, maybe about the same level as injection, but not as good as IV.
caution is highly warranted due to the delicate tissues involved and the risk of infection.