TINNITUS SUPPRESSION BY INTRAVENOUS LIDOCAINE IN RELATION TO ITS PLASMA-CONCENTRATION

In a double-blind controlled trial in nine patients with tinnitus we m easured the lidocaine plasma concentrations during and after intraveno us administration of lidocaine or placebo and scored the level of tinn itus on a visual analog scale. No patient showed any effect during the placebo infusion. Administration of lidocaine resulted in total suppr ession or suppression to a non-annoying level of tinnitus in five pati ents, slight suppression but still annoying tinnitus in two patients, and worsening tinnitus in one patient. No effect of lidocaine was obse rved in one patient. Most relief was obtained at plasma concentrations between 1.5 and 2.5 mug/ml. In this concentration range a significant (p < 0.05) effect of lidocaine on tinnitus was observed. However, not able side effects were observed at plasma concentrations greater than 2.0 mug/ml. The effect persisted until plasma levels of about 0.5 mug/ ml were reached. A large variability in the effects existed because of variations in lidocaine kinetics and because of the presumed psycholo gic components of tinnitus.