Clarence W. Olsen, M.D.
Procaine was introduced as a local anesthetic with advantage over cocaine, especially as regards relative freedom from dangerous central effects. It [now] appears that when procaine hydrochloride is injected intravenously, the indications of a central effect are more emphatic when the solution is given rather rapidly.
Probably some of the central effects of procaine can be obtained with local infiltration. This is, of course, generally admitted when untoward results occur, but it should also be considered in connection with the favorable effects. Macpherson recently expressed the idea that in some cases we are getting the beneficial effects of procaine injection through central action even though the injection is purposely given at or near the site of the pain.
Olsen, Clarence W.
"The Central Action of Procaine,"
Medical Arts and Sciences: A Scientific Journal of the College of Medical Evangelists:
4, Article 7.
Available at: http://scholarsrepository.llu.edu/medartssciences/vol2/iss4/7