Local anesthetics: effect of pH on activity.

Lidocaine and dibucaine are more effective in neutral than in alkaline solution when tested on the nonmyelinated fibers of the desheathed vagus nerve of the rabbit. Procaine, however, is more effective in alkaline solution. The activity of benzocaine is unaffected by pH. Both the charged and uncharged forms of local anesthetics thus seem capable of blocking conduction.