A controlled study of the suppression of tinnitus by lidocaine infusion: (relationship of therapeutic effect with serum lidocaine levels).

The relationship between serum lidocaine levels and tinnitus relief was assessed in 5 patients during intermittent intravenous infusions of the drug. Experiments were conducted under controlled conditions in that neither the attending physician nor the patient was aware of whether active drug or placebo was being infused at any particular time. A significant relationship between serum level and effect was observed in two patients. In the remaining patients this relationship was not readily apparent but there was still a trend for a better response to be seen at higher levels. A satisfactory response was generally seen at levels above 1 microgram/ml. The results are consistent with the hypothesis that the transient nature of the symptomatic relief caused by lidocaine is related to the fast clearance of the drug from the body.