Increased efficacy and toxicity of lidocaine in patients on beta-blockers

The greatest differences in ventricular arrhythmias and adverse effects of lidocaine observed in this study were between patients on both lidocaine and a beta-adrenoceptor blocking agent and those on neither drug. Although free fractions of lidocaine and methylglycylxylidine tended to be higher in patients on beta-adrenoceptor blocking agents, this difference was not significant nor were any other differences in serum drug levels observed.