Simple Method for Maintaining Serum Lidocaine Levels in the Therapeutic Range

• Lidocaine hydrochloride is commonly infused intravenously to prevent ventricular arrhythmias. In some patients, elevations in serum lidocaine levels can cause serious toxic effects. In a group of 19 patients given a constant infusion of lidocaine, we confirmed the observation that serum lidocaine levels rose significantly between four and 24 hours after initiation of therapy. One of these patients manifested a toxic reaction to lidocaine. The lidocaine infusion rate was modified in a second group of 32 patients on the basis of the four-hour serum level. In these patients, after dosage adjustment, the mean lidocaine level did not rise, and all levels remained within the 2- to 4-mg/L therapeutic range at 24 hours. Without dosage adjustment, half of these levels would have fallen outside the desired range. A simple formula can be used to adjust prophylactic lidocaine infusion rates to attain levels that remain therapeutic, yet nontoxic.

(Arch Intern Med