Lidocaine infusions: effect of duration and method of discontinuation on recurrence of arrhythmias and pharmacokinetic variables.

The effect of abrupt versus gradual discontinuation of lidocaine hydrochloride infusion on the incidence of recurrent ventricular arrhythmia and on lidocaine pharmacokinetics was studied. Twenty-nine patients with documented myocardial infarction receiving no other antiarrhythmic drugs and having no evidence of congestive heart failure, liver disease or renal failure were randomly assigned to one or two groups: Group 1--lidocaine infusion was abruptly discontinued after a course of therapy, and Group 2--lidocaine infusion was tapered over a three-hour period. Lidocaine blood levels were measured at the abrupt discontinuation of an infusion or the initiation of tapering and three hours later. Cardiac rhythms were monitored until patients were transferred from the coronary care unit. Three of 18 patients in Group I and two of 11 patients in Group 2 had recurrent ventricular arrhythmias at least 12 hours after idocaine infusion was stopped. The duration of infusion did not correlate with the recurrence of ventricular arrhythmia. In patients infused with lidocaine for 36 hours or less, apparent body clearance was significantly faster than that in patients infused with lidocaine for longer than 36 hours (p less than 0.01). There was no difference in the incidence of recurrent ventricular arrhythmias when comparing abrupt cessation of lidocaine with three-hour tapering. Lidocaine infusion rates may have to be decreased after 36 hours to avoid accumulation of the drug.