Efficacy of lidocaine in preventing primary ventricular fibrillation within 1 hour after a 300 mg intramuscular injection. A double-blind, randomized study of 300 hospitalized patients with acute myocardial infarction.

The effectiveness of intramuscular lidocaine in preventing in-hospital primary ventricular fibrillation within 1 hour after injection of the drug in patients with acute myocardial infarction was assessed in a double-blind randomized study performed in 300 such patients admitted within 6 hours of myocardial infarction. Six of 147 patients treated with 300 mg of intamuscular lidocaine had ventricular fibrillation compared with 4 of 153 control subjects. The lidocaine blood level of the patients who experienced ventricular fibrillation was 1.4 +/- 0.7 microgram/ml (mean +/- standard deviation) at the time of fibrillation, a value not significantly different from that of treated patients who did not experience fibrillation. Lidocaine blood levels in the latter were 1.9 +/- 1.1, 2.1 +/- 1.1, 2.1 +/- 1.1 and 1.7 +/- 0.7 microgram/ml, respectively, 7, 15, 30 and 60 minutes after injection. In this study intramuscular lidocaine was ineffective in preventing ventricular fibrillation, possibly because the given dose, 300 mg, prevented attainment of adequqte blood levels of the drug.