The effect of a single oral dose of propranolol (120 mg) on essential tremor was investigated in a double-blind, placebo-controlled study in 26 patients. Hand tremor was recorded by means of accelerometers, and its frequency and amplitude calculated by using spectrum analysis. Recordings were made before and 1 1/2 hours after drug or placebo administration. Pretreatment tremor ranged from 4.2 to 9.6 Hz (median, 6.9 Hz) in frequency and from 0.002 to 1.33 cm (median, 0.014 cm) in amplitude. Neither propranolol nor placebo affected the frequency of the underlying tremor. The amplitude of tremor was reduced by 43 ± 11% (SEM) after propranolol (p <0.01) and by 12 ± 8% after placebo (NS). The reduction observed after propranolol was significantly greater than that observed after placebo. The tremor response after propranolol correlated negatively with baseline frequency and positively with pretreatment amplitude, duration of tremor, and age of the patient. No significant relationships could be found between tremor response, serum propranolol levels, and degree of cardiac beta blockade as assessed by the inhibition of standing tachycardia. There was a clear tendency for patients with small tremor amplitude (less than 0.006 cm hand displacement) to show the least satisfactory response to propranolol. These results indicate that a single oral dose of propranolol is effective in producing a rapid and marked reduction of essential tremor. Measurement of pretreatment amplitude and frequency might be useful in predicting the therapeutic outcome in these patients.
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