Interaction between lidocaine hydrochloride (with and without adrenaline) and various irrigants: A nuclear magnetic resonance analysis

Abstract

Background: Interaction between local anesthetic solution, lidocaine hydrochloride (with and
without adrenaline), and root canal irrigants such as sodium hypochlorite (NaOCl), ethylene
diamine tetra-acetic acid (EDTA), and chlorhexidine (CHX) has not been studied earlier.
Hence, the purpose of this in vitro study was to evaluate the chemical interaction between 2%
lidocaine hydrochloride (with and without adrenaline) and commonly used root canal irrigants,
NaOCl, EDTA, and CHX.
Materials and Methods: Samples were divided into eight experimental groups: Group
I-Lidocaine hydrochloride (with adrenaline)/3% NaOCl, Group II-Lidocaine hydrochloride
(with adrenaline)/17% EDTA, Group III- Lidocaine hydrochloride (with adrenaline)/2% CHX,
Group IV-Lidocaine hydrochloride (without adrenaline)/3% NaOCl, Group V-Lidocaine
hydrochloride (without adrenaline)/17% EDTA, Group VI-Lidocaine hydrochloride (without
adrenaline)/2% CHX, and two control groups: Group VII-Lidocaine hydrochloride (with
adrenaline)/deionized water and Group VIII-Lidocaine hydrochloride (without adrenaline)/
deionized water. The respective solutions of various groups were mixed in equal proportions
(1 ml each) and observed for precipitate formation. Chemical composition of the formed
precipitate was then analysed by nuclear magnetic resonance spectroscopy (NMR) and
confirmed with diazotation test.
Results: In groups I and IV, a white precipitate was observed in all the samples on mixing the
respective solutions, which showed a color change to reddish brown after 15 minutes. This precipitate
was then analysed by NMR spectroscopy and was observed to be 2,6-xylidine, a reported toxic
compound. The experimental groups II, III, V, and VI and control groups VII and VIII showed no
precipitate formation in any of the respective samples, until 2 hours.
Conclusion: Interaction between lidocaine hydrochloride (with and without adrenaline) and
NaOCl showed precipitate formation containing 2,6-xylidine, a toxic compound.
Key Words: Lidocaine hydrochloride, precipitate, sodium hypochlorite, 2,6-xylidine