Comparison of Methyllidocaine and Lidocaine on Arrhythmias Produced by Coronary Occlusion in the Dog

Methyllidocaine, a quarternary ammonium derivative of lidocaine, was tested as a treatment for the ventricular ectopic beats occurring in unanesthetized dogs 24 hours after two-stage ligation of the anterior descending branch of the left coronary artery. The electrocardiogram (lead II) and electroencephalogram were recorded. Methyllidocaine (4 and 8 mg/kg) injected i.v. during a 1-min period produced a significant reduction in ectopic beats with no significant increase in EEG activity. Lidocaine (4 and 8 mg/kg) administered similarly caused similar antiarrhythmic effects but produced a significant increase in EEG activity. A dose of 8 mg/kg caused tonic-clonic seizures in three of five dogs. Both drugs were also given i.v. (15 mg/kg) to unanesthetized cats. Methyllidocaine did not induce convulsions in four of four animals whereas lidocaine induced convulsions in three of three animals. It is concluded that methyllidocaine is as effective an antiarrhythmic agent as lidocaine but does not possess the central nervous system excitatory actions observed with lidocaine.