Abstract
Lidocaine and its two metabolites, monoethylglycinexylidide and glycinexylidide, were synthesized and their pKa values determined. Temperature markedly affected pKa values. Colorimetric determination of these compounds was studied and a flow chart for determination is shown. Hydrolysis percentages in solution as a function of time were checked at various pH and temperatures. The result showed that lidocaine was stable at all pH regions, and monoethylglycinexylidide and glycinexylidide were hydrolyzed to some extent in acid and alkaline conditions. The phenomena of ortho and steric effects were applied to elucidate the above results. It may be considered from the present in vitro experiments that monoethylglycinexylidide is a major intermediate for hydrolysis to xylidine from lidocaine in vivo.
