A COMPARISON OF DEPTH OF ANESTHESIA AND TOXICITY OF TWO AND FOUR PER CENT PROCAINE HYDROCHLORIDE SOLUTION

1. An objective experimental laboratory procedure for comparing depth of anesthesia after administration of different local anesthetic agents is described.

2. Experimental and clinical tests are reported corroborating the applicability of such a method in comparing intensity of anesthesia for different concentrations of procaine hydrochloride.

3. The results of this study indicate a greater depth of anesthesia of the dental pulp following the submucous administration of 4 per cent procaine hydrochloride solution as compared with the 2 per cent solution with both solutions containing Neo-Synephrine 1:2,500.

4. Toxicity of procaine hydrochloride without added vasoconstrictor is not materially dependent upon concentration in laboratory animals when 2 and 4 per cent concentrations are used, the increase in toxicity being less than 10 per cent when the concentration is increased from 2 to 4 per cent, and drug amounts are kept constant.

5. The theory of the "geometric ratio of increase in toxicity of procaine" is untenable in laboratory animals when death is used as an end point.