Lidocaine should be used with caution in patients receiving agents structurally related to local anaesthetics, since the toxic effects are additive.
Specific interaction studies with local anaesthetics and class III antiarrhythmic drugs have not been carried out, but caution should be observed.
Drugs that reduce the clearance of lidocaine (e.g. cimetidine or beta-blockers) may cause potentially toxic plasma concentrations when lidocaine is given in repeated high doses over a long time period. Such interactions should be of no clinical importance following short-term treatment with lidocaine at recommended doses.