Table 1: Molecular weight, lipid solubility, pKa, and potency of local anesthetics [3, 1620].

MW (g/mol) (base form)Lipid solubility (log [octanol/buffer partition coefficient]) at pH 7.4pKa (−log Ka) at 36°CPotency*

Levobupivacaine2882.539 8.1 8
Ropivacaine2742.0608.16
Lidocaine2341.6337.82
Mepivacaine2461.3227.71.5

MW: molecular weight.
Ka: dissociation constant.
*Data derived from C fibers of isolated rabbit vagus and sciatic nerve [3, 17, 20].