Hypoglycaemia with manifest clinical symptoms has been observed in four patients with cardiac insufficiency after infiltration of high doses of lidocaine prior to surgery. The depressing influence of lidocaine on blood glucose levels has also been seen in six out of 12 patients to whom a pacemaker was implanted in local anaesthesia. The interaction between hepatic glucose- and lidocaine-metabolism could possibly be responsible for this effect. Therefore the evaluation of blood glucose level and iv. administration of glucose is advisable in patients with systemic toxic reactions following lidocaine overdosage to avoid unnecessary symptomatic therapy.