Increased Alpha-1-Acid Glycoprotein and Lidocaine Disposition in Myocardial Infarction

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Abstract
In 15 patients with confirmed myocardial infarction, .alpha.1-acid glycoprotein rose significantly from 117 mg/dl at admission to 140 mg/dl at 36 h (P < 0.01), but not in 15 age- and sex-matched patients with chest pain only. Patients (12) were given prolonged infusions of lidocaine (2 mg/min). In patients with myocardial infarction, the rise in plasma .alpha.1-acid glycoprotein concentration was associated with increased lidocaine binding and a rise in total lidocaine concentrations between 12 and 48 h (P < 0.05). Due to the binding changes the rise in free drug concentration (31.2%) was significantly less than the 56.3% rise in total drug level (P < 0.05). No changes in .alpha.1-acid glycoprotein or lidocaine disposition were seen between 12 and 48 h in the control subjects. The rise in .alpha.1-acid glycoprotein after myocardial infarction is associated with lidocaine accumulation, but increased plasma binding attenuates the rise in free drug. The toxicologic implications of lidocaine accumulation may exaggerate and the therapeutic monitoring of total plasma levels may be misleading.