Intramuscular
lidocaine administration is known to produce blood concentration levels considered to be therapeutic for prevention of
premature ventricular contractions. This double blind study was designed to study the effect of intramuscular
lidocaine in the prevention of
PVC's in acute
myocardial infarction. Forty-six patients with confirmed acute
myocardial infarction, without
congestive heart failure,
shock, or major arrhythmias were admitted to the trial. Twenty-one patients received 4.5 mg. per kilogram of intramuscular
lidocaine and 25 patients received placebo in the deltoid muscle within 14 hours of the onset of symptoms. Rhythm strips of 2 minutes' duration, blood pressure, heart rate, and blood specimens for blood concentration levels were obtained prior to and 5, 10, 15, 30, 60, 90, and 120 minutes after injection. The mean blood concentration level of
lidocaine was 1.81 +/- 0.22 mug per milliliter at 5 minutes, reached a maximum of 2.18 +/- 0.22 mug per milliliter
at 10 minutes, and was still 0.81 +/- 0.05 at 120 minutes. Analysis of rhythm strips revealed that only three of 21 patients (14 per cent) in the intramuscular
lidocaine group developed at least one
PVC as compared to 13 of 25 (52 per cent) in the placebo group (p less than 0.0005). No significant toxic effects were noted. This study suggests that intramuscular
lidocaine may significantly reduce potentially fatal arrhythmias in early phases of acute
myocardial infarction.