Abstract
Although the use of an electric field to force drugs into the skin has been known for many decades, surprisingly few experiments have been performed with local anesthetics. That the unbroken skin can be anesthetized by the electrophoresis of drugs into the skin has been known for many years, but this method has not been developed in the light of the modern theory of electrolytes.
It is of interest both theoretically in connection with electrokinetic properties of the skin, and practically in hay fever, to determine if the anesthetization of a small area is without essential influence on the development of moderately or markedly positive skin reactions.
By the use of an electrode especially designed to anesthetize a large number of small areas of the skin simultaneously, it has been possible to make intradermal tests with ragweed, timothy, dust, and other inhalants without any discomfort to the patient. Anesthesia lasting sufficiently long to perform skin tests can be obtained after 10 to 15 minutes electrophoresis of (1) procaine base in alcoholic or acetone solution, (2) butyn base, (3) cocaine base, (4) procaine hydrochloride, of various concentrations. Some effect was obtained with procaine borate. Agar jellies of the foregoing anesthetics were also effective. Control tests of allergens without the anesthetic have shown with few exceptions only the variability in skin reactions usually found on comparing 2 different skin sites. In fact, because of the anesthesia, the cooperation of the patient is more than usual and the fine needle may be inserted with greater care, Of the anesthetics employed, procaine base containing a trace of alkali has given the most consistent results with current densities of approximately 0.5 milliampere.
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