Blood Lidocaine Levels and Kinetics following High-Dose Intramuscular Administration

Abstract

In order to evaluate further the potential benefit of prophylactic intramuscular lidocaine administration in coronary artery disease, 24 patients with suspected acute myocardial infarction were given an intramuscular injection of lidocaine (10% solution) in the deltoid and gluteal muscles on consecutive days. Twelve patients received an intermediate dose (4 mg/kg), and 12 received a high dose (6 mg/kg) of lidocaine, and blood lidocaine levels were measured over a 4-hour study period. Intradeltoid injection produced higher blood lidocaine levels and more rapid development of peak blood levels than did intragluteal injection. Administration of high-dose lidocaine (average dose 450 mg) into the deltoid muscle produced the ideal combination of rapid peak blood levels (6.5 µg/ml ± 2.1 SEM at 5 min) and persistence of therapeutic levels (>1.5 µg/ml) for over 2 hours. Although drowsiness, paresthesias, slurred speech, and tinnitus occurred in seven of the 12 patients in the high-dose group, no major neurotoxicity, such as grand mal seizures, were observed, nor was there evidence of hypotension or increase in atrioventricular block. Prophylactic administration of high-dose 10% lidocaine into the deltoid muscle appears to have potential for reducing the early mortality following acute myocardial infarction.