Table 1.

Molecular weight, lipid solubility, pKa, and potency of local anesthetics [3, 16–20].

	MW (g/mol) (base form)	Lipid solubility (log [octanol/buffer partition coefficient]) at pH 7.4	pKa (−log Ka) at 36°C	Potency∗
Levobupivacaine	288	2.539	8.1	8
Ropivacaine	274	2.060	8.1	6
Lidocaine	234	1.633	7.8	2
Mepivacaine	246	1.322	7.7	1.5

MW: molecular weight.

Ka: dissociation constant.

^∗Data derived from C fibers of isolated rabbit vagus and sciatic nerve [3, 17, 20].