Chemical stability of lignocaine (lidocaine) and adrenalin (epinephrine) in pH-adjusted parenteral solutions.

Recent clinical studies have shown that alkalinizing lignocaine (lidocaine) solutions is an effective way of shortening the time of onset and increasing the duration of anaesthesia. However, alkalinizing lignocaine solutions raises the problem of the stability of these preparations. Moreover, the adrenalin usually associated with it is unstable in alkalinized solutions designed for peridural injection. This study was performed to define the range of pH over which lignocaine and adrenalin in commercial solution is stable. The results indicate that it is possible to alkalinize lignocaine solutions and that the solutions prepared are stable for at least 6 h.