Effect of Some Vasoconstrictors on Intradermal Anesthesia

¹ Pharmacology Section, Sterling-Winthrop Research Institute, Rensselaer, New York

Intradermal anesthetic activity and duration of anesthesia were determined in guinea pigs by the method of Bülbring and Wajda.

The addition of graded concentrations of epinephrine (1:25,000 to 1:400,000) increased the local anesthetic activity of a solution of 0.25 per cent propoxycaine HCl, the greatest effect being obtained with the highest concentration.

Epinephrine, levarterenol, and levo-nordefrin increased the duration of propoxycaine anesthesia. Linear dose-effect curves were obtained by plotting the average duration in minutes against the log of the vasoconstrictor concentration in solutions of 0.25 per cent propoxycaine.

In solutions containing epinephrine 1:100,000, changing the concentration of procaine from 0.5 to 4.0 per cent or that of propoxycaine from 0.25 to 2.0 per cent did not greatly prolong the duration of anesthesia.

The duration of action of the procaine solutions was shorter than that of the propoxycaine solutions.

These results show that in mixtures of propoxycaine (or procaine) and vasoconstrictors, in concentrations similar to those found in commercial dental anesthetic solutions, the duration of local anesthesia is influenced much more by the concentration of the vasoconstrictor than by that of the local anesthetic.