A new method for constant plasma drug concentrations: application to lidocaine.

Optimal intravenous drug therapy often requires the rapid achievement and maintenance of therapeutic plasma drug concentrations. Simple regimens (single bolus and maintenance infusion) can produce wide variations in plasma drug concentrations early in therapy, and more complex regimens require a series of precisely timed infusion rate changes to minimize such variability. A new simple method of delivering an infusion produces a delivery rate that declines exponentially, thereby providing stable plasma concentrations after a bolus dose. The method requires no specialized equipment and no intervention once started. The method has been tested both ex vivo and in normal volunteers receiving lidocaine. Stable lidocaine plasma concentrations are rapidly achieved and maintained within the therapeutic range. Further evaluation of this approach in patients is indicated.