pKa of lidocaine:
Lidocaine hydrochloride is very soluble in water and alcohol and soluble in chloroform, but it is insoluble in ether. Lidocaine hydrochloride has a pKa of 7.86. Gebauer et al. developed a method for the study of lidocaine and oxycodone stability in a rectal gel.
The dissociation constants (pKa) for popular local anesthetics used in dentistry are:
Mepivacaine 7.6
Etidocaine 7.7
Lidocaine 7.9
Prilocaine 7.9
Bupivacaine 8.1
Tetracaine 8.5
Procaine 9.1
Ref: Monheim’s Local anesthesia 1st  ed page no 130
8.1
8.9
7.8
7.6