Intramuscularly and orally administered lidocaine in the treatment of ventricular arrhythmias in acute myocardial infarction

An intramuscular injection of 2.5 ml of 10 percent lidocaine was given to 26 cardiac patients. An effective mean plasma level (1 mg/liter or more) was reached in 5 minutes and persisted for 120 minutes; the highest mean level (2.2 mg/liter, SEM ± 0.18) was reached after 30 minutes. In 15 patients who sustained an acute myocardial infarction with premature ventricular contractions, the frequency of premature ventricular contractions was continuously recorded with an arrhythmia monitor. After intramuscular administration of lidocaine the number of premature ventricular contractions decreased by an average of 75 percent. Oral administration of 250 mg of lidocaine to 7 other patients resulted in low plasma levels and had little effect on premature ventricular contractions. No serious adverse effects on heart rate, atrioventricular conduction or blood pressure were encountered in any patient, including 5 with myocardial infarction and various degrees of heart block. It is believed that intramuscular administration of lidocaine could be useful in the prevention of sudden death due to ventricular fibrillation in the “precoronary” phase.