Zonisamide for essential tremor

Zonisamide in Parkinson's disease: a current update

Parkinson's disease (PD) is a progressive neurodegenerative disease due to the depletion of the neurotransmitter dopamine in basal ganglia. There is a scarcity of available therapies for motor and non-motor symptoms of PD. Zonisamide (ZNS) may be one such potential candidate to alleviate PD symptoms. It was serendipitously found to be useful for PD in a patient with both epilepsy and PD. Since then, there have been many clinical trials, case series, observational studies, and case reports published supporting the efficacy of ZNS in PD. This review focuses on the efficacy and usefulness of ZNS in various motor and non-motor symptoms of PD. A predefined inclusion and exclusion criteria were used for the search protocol and databases searched were PubMed, Cochrane Library, Ovid, and clinicaltrials.gov. Most of the randomized clinical trials used UPDRS III as the primary efficacy point and showed positive results favouring ZNS. This review shows that there is evidence of the efficacy of ZNS in motor symptoms as an adjunctive therapy to levodopa, but for non-motor symptoms, the evidence is lacking and needs further investigation.

Mechanisms and Pharmacotherapy for Ethanol-Responsive Movement Disorders

Ethanol-responsive movement disorders are a group of movement disorders of which clinical manifestation could receive significant improvement after ethanol intake, including essential tremor, myoclonus-dystonia, and some other hyperkinesia. Emerging evidence supports that the sensitivity of these conditions to ethanol might be attributed to similar anatomical targets and pathophysiologic mechanisms. Cerebellum and cerebellum-related networks play a critical role in these diseases. Suppression of inhibitory neurotransmission and hyper-excitability of these regions are the key points for pathogenesis. GABA pathways, the main inhibitory system involved in these regions, were firstly linked to the pathogenesis of these diseases, and GABA_A receptors and GABA_B receptors play critical roles in ethanol responsiveness. Moreover, impairment of low-voltage-activated calcium channels, which were considered as a contributor to oscillation activity of the nervous system, also participates in the sensitivity of ethanol in relevant disease. Glutamate transporters and receptors that are closely associated with GABA pathways are the action sites for ethanol as well. Accordingly, alternative medicines aiming at these shared mechanisms appeared subsequently to mimic ethanol-like effects with less liability, and some of them have achieved positive effects on different diseases with well-tolerance. However, more clinical trials with a large sample and long-term follow-ups are needed for pragmatic use of these medicines, and further investigations on mechanisms will continue to deepen the understanding of these diseases and also accelerate the discovery of ideal treatment.

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.