[Effect of membrane-effective drugs (anti-arrhythmia agents) on acoustically evoked brain-stem potentials]

Lidocaine, Mexiletine, Procainamide, and Phenytoin were administered intravenously to anaesthesized rabbits. BERA alterations showed two different patterns. If the intoxication dose was exceeded, amplitude depression, threshold elevation, desynchronization, and severe cumulative prolongation of all latencies and interpeak latencies appeared. Below this dose Lidocaine and Mexiletine induced a single, reversible, dose related, cumulative prolongation of all latencies and interpeak latencies. Procainamide induced counterrelated shiftings of interpeak latencies I-III and III-V, whereas Phenytoin showed no influence. One should, therefore, take into account these effects when BERA is used clinically, since otherwise serious errors can occur. On the other hand, there are diagnostic and therapeutic aspects for the tinnitus patient.