Depression of essential tremor by alpha-adrenergic blockade

Current and Future Neuropharmacological Options for the Treatment of Essential Tremor

BACKGROUND

Essential Tremor (ET) is likely the most frequent movement disorder. In this review, we have summarized the current pharmacological options for the treatment of this disorder and discussed several future options derived from drugs tested in experimental models of ET or from neuropathological data.

METHODS

A literature search was performed on the pharmacology of essential tremors using PubMed Database from 1966 to July 31, 2019.

RESULTS

To date, the beta-blocker propranolol and the antiepileptic drug primidone are the drugs that have shown higher efficacy in the treatment of ET. Other drugs tested in ET patients have shown different degrees of efficacy or have not been useful.

CONCLUSION

Injections of botulinum toxin A could be useful in the treatment of some patients with ET refractory to pharmacotherapy. According to recent neurochemical data, drugs acting on the extrasynaptic GABAA receptors, the glutamatergic system or LINGO-1 could be interesting therapeutic options in the future.

A multicenter randomized crossover multiple-dose comparison study of arotinolol and propranolol in essential tremor

BACKGROUND

A new medication is needed to treat essential tremor. Preliminary evidence suggests that arotinolol may be effective in the treatment of this disorder.

OBJECTIVE

To study the effect of arotinolol and propranolol in a crossover, multiple dose comparative trial of patients with essential tremor.

PATIENTS AND METHODS

One hundred and seventy-five outpatients, with essential tremor were included in the study; 161 patients completed the study. Patients were identically evaluated at eight consecutive visits. The study consisted of two treatments, which were arranged according to a crossover design that evaluated the dose of each (arotinolol 10 mg per day and propranolol 40 mg per day, arotinolol 20 mg per day and propranolol 80 mg per day, arotinolol 30 mg per day and propranolol 160 mg per day). Each course of treatment lasted 6 weeks. Major outcome evaluations consisted of a self-reported disability scale, and motor performance score obtained before drug intake and 14 days after each treatment. The treatment effects were evaluated by analysis of variance using the Hills-Armitage test.

RESULTS

Arotinolol was found to be as effective as propranolol at reducing tremor. Drug effects as evaluated using motor-task performance scores revealed that arotinolol had a more significant effect than propranolol.

CONCLUSIONS

Arotinolol may be more useful than propranolol for the treatment of essential tremor.

Acute and chronic effects of clozapine in essential tremor

Patients with essential tremor (ET) may not respond to commonly used drugs. Clozapine, an atypical neuroleptic drug, has been reported to improve postural Parkinson's disease tremor clinically resembling ET. The effects of a single dose of 12.5 mg clozapine and placebo were evaluated in a randomized, double-blind, crossover study in 15 drug-resistant patients with ET. Patient responders with more than 50% improvement after a single dose of clozapine subsequently received the drug (39+/-9 mg up to 50 mg) unblinded for a period of 15.8+/-7.7 months. Tremor was effectively reduced by a single dose of clozapine in 13 of 15 patients (p <0.01). Sedation was the only side effect reported during the clozapine test; however, the time course of sedation and of the antitremor effect were not coincident. A significant reduction of tremor was reported with chronic clozapine treatment (p <0.01) with no tolerance to drug antitremor effect, whereas sedation markedly decreased after 6-7 weeks of therapy. No clozapine-induced hematologic side effects were observed in our cohort of patients during long-term treatment. Our results suggest that in selected drug-resistant ET cases, clozapine should be considered before resorting to neurosurgical options.

Hereditary essential tremor in Buenos Aires (Argentina)

A descriptive trial of essential tremor in Buenos Aires city is proposed. It may be considered as the first one like this in Latin America. During a 15 year period, sixteen families with essential tremor diagnosis have been examined, making a total of 39 patients (20 males and 19 females). The disease was basically studied from its semiological, clinico-evolutive and therapeutical view point, following a protocol. Our results indicate -- a. The clinico-evolutive characteristics: its frequency (according to race, sex, social status, age of beginning and physiopathological type), morbidity and mortality, evolution, prognosis, triggering factors, longevity and multiparity. b. The different treatment given to our patients with discussion of their pharmacokinetic and pharmacodynamic basis and evaluation of the best responses. In this matter, it is concluded that both primidone (750 mg/daily) and/or propranolol (160-240 mg/daily) are undeniably the drugs of first choice for the treatment of this disease. A comparison of the clinico-therapeutic features of this tremor in Buenos Aires and other cities is done. The study of this syndrome in Buenos Aires does not give different results from those obtained in Europe and USA.

Effect of acute and chronic oral administration of alfuzosin on baroreflex function and tremor in man

1. The effects of the acute and chronic administration of the alpha 1-adrenoceptor antagonist alfuzosin (5 mg twice daily for 7 days) on baroreflex function, physiological tremor and sedation (visual analogue scale) were investigated in six healthy volunteers. 2. Phenylephrine-systolic pressure dose-response curves were shifted (P less than 0.05) to the right by alfuzosin compared with placebo on day 1, and on day 8 prior to the administration of alfuzosin indicating significant alpha-adrenoceptor blockade over 24 h with 5 mg twice daily administration. 3. Baroreflex sensitivity (delta R-R ms mmHg-1 systolic arterial pressure) was reduced (P less than 0.05) by alfuzosin compared with placebo on day 1 (13.8 +/- 2.6 vs 20.6 +/- 3.6 ms mmHg-1) and on day 8 (13.4 +/- 1.7 vs 21.1 +/- 2.7 ms mmHg-1). 4. Maximum power (microV2) or frequency (Hz) of physiological tremor did not change 2 h after alfuzosin administration on day 1 (13.7 +/- 4.4 microV2, 9.2 +/- 0.3 Hz) or day 8 (11.5 +/- 4.3 microV2, 10.0 +/- 0.4 Hz) compared with placebo on day 1 (16.9 +/- 7.5 microV2, 10.0 +/- 0.4 Hz) and day 8 (17.3 +/- 5.7 microV2, 10.2 +/- 0.8 Hz). 5. Alfuzosin 5 mg twice daily did not cause sedation on day 1 or day 8. 6. In conclusion the reduction in baroreflex sensitivity with the alpha-adrenoceptor antagonist alfuzosin may contribute to its antihypertensive activity in reducing the reflex tachycardia associated with its hypotensive action.

Effects of azepexole and clonidine on baroreceptor mediated reflex bradycardia and physiological tremor in man

The effects of oral administration of azepexole 10 mg, clonidine 300 micrograms and placebo on baroreceptor mediated reflex bradycardia and physiological tremor were investigated in six healthy volunteers. Both azepexole and clonidine reduced (P less than 0.05) systolic (120.5 +/-2.5 to 105.0 +/- 3.3 mm Hg; 115.8 +/- 2.6 to 104.7 +/- 2.8 mm Hg respectively) and diastolic (52.5 +/- 2.6 to 47.2 +/- 1.4 mmHg; 53.7 +/- 1.6 to 49.0 +/- 1.5 mmHg respectively) pressure when compared to placebo and to pre-treatment values. This reduction in pressure was not accompanied by a change in heart rate. Both azepexole and clonidine enhanced (P less than 0.05) baroreflex sensitivity to increases in systolic arterial pressure with phenylephrine. Clonidine facilitated (P less than 0.05) baroreflex sensitivity during the strain phase of the Valsalva manoeuvre, whereas azepexole reduced it (P less than 0.05). Neither clonidine nor azepexole altered finger tremor when compared to placebo or pre-treatment values. Azepexole produced (P less than 0.05) sedation compared to placebo but not when compared to pre-treatment values. Clonidine caused significant increases in sedation when compared to both placebo and to pre-treatment values. The differences between azepexole and clonidine may be due to the greater specificity of azepexole for the alpha 2-adrenoceptor than clonidine.

Differential effects of alpha-adrenoceptor blockade on essential, physiological and isoprenaline-induced tremor: evidence for a central origin of essential tremor

Intravenous thymoxamine reduced the power of essential tremor but increased that of physiological and isoprenaline-induced tremor. These findings indicate that essential and physiological tremor have dissimilar pathophysiological mechanisms. They also suggest that central adrenergic mechanisms are involved in the pathophysiology of essential tremor and that isoprenaline-induced tremor is not a good model of essential tremor. Furthermore, alpha-adrenoceptor blockers may be a useful therapy for essential tremor.

Adrenergic beta-receptor sensitivity in essential tremor

Adrenergic beta-receptor sensitivity of six male patients with essential tremor and six age-matched normal controls was assessed by measuring the response in the heart rate and postural tremor to incremental injections of the adrenergic beta-agonist isoprenaline. The relative increase in heart rate and tremor in essential tremor patients did not differ from that in normal controls. It is concluded that no major abnormality is likely to exist in the peripheral adrenergic beta-receptor sensitivity in essential tremor.