Relationship between alpha-1-acid glycoprotein concentration and plasma protein binding of mexiletine after acute myocardial infarction. Comparative study with disopyramide.

The influence of alpha-i-acid glycoprotein (AAG.) concentration on plasma protein binding of mexiletine and of disopyramide were investigated in patients with acute myocardial infarction and other heart disorders. The following results were obtained:(1) There was a linear relationship between the dose and plasma total concentration of mexiletine. There was no significant correlationship between the dose and plasma total concentration of disopyramide.(2) There was no significant correlationship between the concentration of AAG and free fraction of mexiletine, and negative correlation was observed between the concentration of AAG and free fraction of disopyramide.(3) No significant differences were observed in patients with acute myocardial infarction and other heart disorders between total plasma concentration and free fraction of mexiletine.There was no significant difference in total plasma concentration of disopyramide between the patients with acute myocardial infarction and other heart disorders. The free fraction in patients with acute myocardial infarction was significantly lower than that in those with other heart disorders (P<0.01).(4) The influence of AAG concentration on free fraction percent of mexiletine was not appreciated. Therefore, we concluded that the monitoring of total plasma concentration of mexiletine was important.