Fig. 2. Measured free fractions of S (−)-bupivacaine (open symbols) and R (+)-bupivacaine (closed symbols) versus plasma α1-acid-glycoprotein (AAG) concentrations. The corresponding lines were obtained by simple linear regression of the free fractions versus the plasma AAG concentrations. Coefficients of determination (R2) for the free fraction vs. plasma AAG concentration relations were 0.52 (P < 0.0001) for S (−)-bupivacaine and 0.55 (P < 0.0001) for R (+)-bupivacaine, respectively.