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 less than 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.