Chapter 9, Problem 9.58PP

Summary Introduction

To determine:

An anesthetic drug between mepivacaine and bupivacaine which will have more of the uncharged form available at physiological $\text{pH}$ that block pain quicker with an explanation.

Introduction:

Mepivacaine and bupivacaine are local anesthetic drugs of the amino ester group used in epidural blocks. They contain an amine functional group, which in its acid form has a positive charge (protonated amine) and in its conjugate base form is neutral.

The equilibrium constant $\left(K_{\text{a}}\right)$ of an acid dissociation reaction depends on the strength of an acid involved in the reaction. The value of $K_{\text{a}}$ is large for strong acids and small for weak acids. In $\text{p}{K}_{\text{a}}$, p means to take the negative log of a number. The $\text{p}{K}_{\text{a}}$ value of acid is calculated by the formula,

$\text{p}{K}_{\text{a}}=-{\log }_{10}{K}_{\text{a}}$