The response of essential tremor to propranolol: evaluation of clinical variables governing its efficacy on prolonged administration.

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Abstract
The factors influencing the response of essential tremor to prolonged administration of propranolol (120 mg daily for two weeks followed by 240 mg daily for a further two weeks) were investigated in a double-blind, cross-over, placebo-controlled study in 16 patients. Hand tremor was assessed by means of accelerometers with off-line computer analysis. Propranolol was found to be superior to placebo only at the higher dosage regimen (240 mg daily). At this dosage, the median reduction in tremor amplitude (as compared to the control value) was by 45%. The response to the drug (expressed as percentage change in tremor amplitude) was correlated positively with the control amplitude (rs = 0.71, p < 0.01) and negatively (but more weakly) with the control peak frequency of tremor (rs = -0.53, p < 0.05). In the patients with hand tremor greater than 6 x 10(-3) cm hand displacement the tremor amplitude was reduced by 65%, as compared to only 17% in patients whose tremor amplitude was below this limit. No statistically significant relationship could be found between percentage change in tremor amplitude and duration of the disorder, age of the patients, degree of cardiac beta-blockade or serum propranolol levels. The results suggest that patients with small tremor amplitude should not be treated with propranolol unless their tremor becomes severely aggravated under conditions of excessive adrenergic discharge.