Suppression of essential tremor by propranolol: correlation of effect with drug plasma levels and intensity of beta-adrenergic blockade

Propranolol was given intravenously to 6 adult patients with essential tremor, using a bolus-infusion regimen for rapid production and maintenance of predicted drug plasma levels. Tremor in the outstretched hand was quantitated by integration of the waveform signal recorded from a miniature accelerometer. Propranolol had no effect on tremor frequency (6 to 8 cps), but it suppressed tremor amplitude in all patients in direct proportion to the drug's plasma concentration and to the intensity of beta-adrenergic blockade produced. Among this group of patients the maximal tremor decrease occurred at plasma levels of about 100 ng per milliliter and varied widely between individuals (18 to 85%), implying that the efficacy of propranolol therapy in essential tremor depends on both the plasma drug level and the innate sensitivity of the disorder in the individual patient.