Comparison of Toxicity of Intravenously Given Local Anesthetic Agents in Man

Twelve unanesthetized volunteers received intravenous infusions of procaine, chloroprocaine, tetracaine, and lidocaine to permit comparison of the systemic toxic effects of the drugs. Administration by vein assured equivalent plasma level of the agents and permitted a controlled dosage simulating one ordinarily used for regional anesthesia. The resulting functional disturbances were relatively minor, yet electrocardiographic tracings indicative of deteriorating cardiac activity were frequently encountered. The electroencephalographic tracings simulated the pattern of those of a person when normally asleep. The spikes typically seen in EEG tracings just before epileptic seizures were absent on the records of two subjects who had convulsions. Lidocaine was most poorly tolerated. Chloroprocaine was tolerated the best, and its low toxicity is considered to be due to its more rapid hydrolysis by plasma cholinesterase.