alpha 1-Acid glycoprotein and plasma lidocaine binding

The relationship between the degree of plasma binding of lidocaine (lignocaine) and the concentration of the acute phase reactant, alpha 1-acid glycoprotein (AAG), is reviewed. Studies in normal subjects and patients with myocardial infarction, renal disease, hepatic failure and receiving antiepileptic drug therapy have all shown a remarkably good relationship between AAG concentration and the binding ratio for lidocaine. In situations where AAG is altered, particularly myocardial infarction, the usual therapeutic range for total plasma lidocaine concentrations may not apply and must be interpreted appropriately. This provides the strongest rationale for monitoring free rather than total drug concentration as an aid in lidocaine therapy.