THE INFLUENCE OF pH ON THE ACTIVITY OF CERTAIN LOCAL ANESTHETICS AS MEASURED BY THE RABBIT'S CORNEA METHOD

1. The anesthetic activities of procaine hydrochloride, procaine borate, butyn, and butesin picrate have been investigated by the rabbit's cornea method.

2. The duration of anesthesia produced by procaine hydrochloride, by procaine borate and by butyn increased with increase of pH. Duration of anesthesia of butesin picrate, on the other hand, was apparently unaffected by changes in pH.

3. When compared with unbuffered or very weakly buffered solutions, at the same pH, i.e., by adjustment with NaOH, buffer salts in concentrations higher than m/100 increased the duration of anesthesia produced by butyn and by procaine hydrochloride.

4. Neither n/8 NaCl, n/8 KCl, n/7 Na₂SO₄, nor n/5 MgSO₄ altered the activity of buffered butyn solutions over the range of pH studied.