Influence of Metoprolol d osage r elease Formulation on the Pharmacokinetic d rug Interaction With Paroxetine

0 to the 24-hour blood draw (AUC 0-24h ) by 4- and 5-fold, respectively for IR, and 3- and 4-fold, respectively, for ER. S/R AUC ratios significantly decreased. These results demonstrate a pharmacokinetic interaction between paroxetine and both formulations of metoprolol. The interaction is greater with R metoprolol, and stereoselective metabolism is lost. This could theoretically result in greater beta-blockade and lost cardioselectivity. The magnitude of the interaction was similar between metoprolol formulations, which may be attributable to low doses/drug input rates employed.