A Pilot Double-Blind Randomized Trial of Perampanel for Essential Tremor

Background

Perampanel is a noncompetitive antagonist of alpha-amino-3-hydroxy-5-methylisoxazole propionic acid glutamate receptors suggested to modulate tremor.

Objectives

To assess the efficacy and tolerability of perampanel for essential tremor.

Methods

This was a double-blind, placebo-controlled, randomized, cross-over trial involving 26 patients titrated to 8 mg/day or a lower maximally tolerated dose as monotherapy or adjunct to antitremor medication. Tremor was assessed at the beginning and end of each 14-week treatment arm. The primary endpoint was change in the videotaped performance subscale of The Essential Tremor Rating Assessment Scale, scored by a blinded rater. Secondary endpoints included change in The Essential Tremor Rating Assessment Scale Activity of Daily Living and Quality of Life in Essential Tremor and Subject Global Impression of Change subscales.

Results

Data are available for 15 and 11 participants who completed placebo and perampanel arms, respectively. Perampanel was superior to placebo on the primary endpoint (P = 0.028), Activity of Daily Living (P = 0.009), and Subject Global Impression of Change (P = 0.016), but not Quality of Life (p = 0.48). Video scores were rated >50% improved in 3/11 on perampanel and 0/15 on placebo. Adverse events were more likely on perampanel (especially at >4 mg/day) than on placebo, leading to withdrawal (36% vs. 10%) and dose reduction (41% vs. 15%). Adverse events more common with perampanel included imbalance/falls (50% vs. 10%), dizziness (36% vs. 10%), and irritability (27% vs. 5%).

Conclusions

These findings suggest that perampanel exerts efficacy for some persons with essential tremor, but this population appears prone to adverse events.

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.

Improving Working Conditions to Promote Worker Safety, Health, and Wellbeing for Low-Wage Workers: The Workplace Organizational Health Study

This paper addresses a significant gap in the literature by describing a study that tests the feasibility and efficacy of an organizational intervention to improve working conditions, safety, and wellbeing for low-wage food service workers. The Workplace Organizational Health Study tests the hypothesis that an intervention targeting the work organization and environment will result in improvements in workers' musculoskeletal disorders and wellbeing. This ongoing study is being conducted in collaboration with a large food service company. Formative evaluation was used to prioritize outcomes, assess working conditions, and define essential intervention elements. The theory-driven intervention is being evaluated in a proof-of-concept trial, conducted to demonstrate feasibility and potential efficacy using a cluster randomized design. Ten worksites were randomly assigned to intervention or control conditions. The 13-month intervention uses a comprehensive systems approach to improve workplace policies and practices. Using principles of participatory engagement, the intervention targets safety and ergonomics; work intensity; and job enrichment. The evaluation will provide a preliminary assessment of estimates of the intervention effect on targeted outcomes and inform understanding of the intervention implementation across worksites. This study is expected to provide insights on methods to improve working conditions in support of the safety and wellbeing of low-wage workers.

Implementing an Integrated Health Protection/Health Promotion Intervention in the Hospital Setting: Lessons Learned From the Be Well, Work Well Study

OBJECTIVE

This study reports findings from a proof-of-concept trial designed to examine the feasibility and estimates the efficacy of the "Be Well, Work Well" workplace intervention.

METHODS

The intervention included consultation for nurse managers to implement changes on patient-care units and educational programming for patient-care staff to facilitate improvements in safety and health behaviors. We used a mixed-methods approach to evaluate feasibility and efficacy.

RESULTS

Using findings from process tracking and qualitative research, we observed challenges to implementing the intervention due to the physical demands, time constraints, and psychological strains of patient care. Using survey data, we found no significant intervention effects.

CONCLUSIONS

Beyond educating individual workers, systemwide initiatives that respond to conditions of work might be needed to transform the workplace culture and broader milieu in support of worker health and safety.

The treatment of tremor

Tremor is a hyperkinetic movement disorder characterized by rhythmic oscillations of one or more body parts. It can be disabling and may impair quality of life. Various etiological subtypes of tremor are recognized, with essential tremor (ET) and Parkinsonian tremor being the most common. Here we review the current literature on tremor treatment regarding ET and head and voice tremor, as well as dystonic tremor, orthostatic tremor, tremor due to multiple sclerosis (MS) or lesions in the brainstem or thalamus, neuropathic tremor, and functional (psychogenic) tremor, and summarize main findings. Most studies are available for ET and only few studies specifically focused on other tremor forms. Controlled trials outside ET are rare and hence most of the recommendations are based on a low level of evidence. For ET, propranolol and primidone are considered drugs of first choice with a mean effect size of approximately 50 % tremor reduction. The efficacy of topiramate is also supported by a large double-blind placebo-controlled trial, while other drugs have less supporting evidence. With a mean effect size of about 90 % deep brain stimulation in the nucleus ventralis intermedius or the subthalamic nucleus may be the most potent treatment; however, there are no controlled trials and it is reserved for severely affected patients. Dystonic limb tremor may respond to anticholinergics. Botulinum toxin improves head and voice tremor. Gabapentin and clonazepam are often recommended for orthostatic tremor. MS tremor responds only poorly to drug treatment. For patients with severe MS tremor, thalamic deep brain stimulation has been recommended. Patients with functional tremor may benefit from antidepressants and are best be treated in a multidisciplinary setting. Several tremor syndromes can already be treated with success. But new drugs specifically designed for tremor treatment are needed. ET is most likely covering different entities and their delineation may also improve treatment. Modern study designs and long-term studies are needed.

Efficacy and safety of carisbamate in patients with diabetic neuropathy or postherpetic neuralgia: results from 3 randomized, double-blind placebo-controlled trials

The results of 3 proof-of-concept studies to evaluate carisbamate's efficacy and safety in treating neuropathic pain are presented. In studies 1 (postherpetic neuralgia, n = 91) and 2 (diabetic neuropathy, n = 137), patients received carisbamate 400 mg/day or placebo for 4 weeks and then crossed over to the other treatment for 4 weeks. In study 3 (diabetic neuropathy, higher carisbamate doses), patients (n = 386) were randomized (1:1:1:1) to receive either carisbamate 800 mg/day, 1200 mg/day, pregabalin 300 mg/day or placebo for 15 weeks. Primary efficacy end point was the mean of the last 7 average daily pain scores obtained on days the study drug was taken, for all 3 studies. Least square mean (95% CI) differences between carisbamate and placebo groups on the primary end point were as follows: study 1: -0.512 (-1.32, 0.29) carisbamate 400 mg/day; study 2: -0.307 (-0.94, 0.33) carisbamate 400 mg/day; and study 3: -0.51 (-1.10, 0.08), carisbamate 800 mg/day; -0.55 (-1.13, 0.04), carisbamate 1200 mg/day; and -0.43 (-1.01, 0.15), pregabalin 300 mg/day. Neither carisbamate (all 3 studies) nor pregabalin (study 3) significantly differed from placebo, although multiple secondary end points showed significant improvement in efficacy with carisbamate in studies 1 and 2. Dizziness was the only treatment-emergent adverse event occurring at ≥10% difference in carisbamate groups versus placebo (study 1: 12% vs. 1%; study 3: 14% vs. 4%; study 2: 1% vs. 2%). Carisbamate, although well tolerated, did not demonstrate efficacy in neuropathic pain across these studies, nor did the active comparator pregabalin (study 3).

Harmaline tremor: underlying mechanisms in a potential animal model of essential tremor

BACKGROUND

Harmaline and harmine are tremorigenic β-carbolines that, on administration to experimental animals, induce an acute postural and kinetic tremor of axial and truncal musculature. This drug-induced action tremor has been proposed as a model of essential tremor. Here we review what is known about harmaline tremor.

METHODS

Using the terms harmaline and harmine on PubMed, we searched for papers describing the effects of these β-carbolines on mammalian tissue, animals, or humans.

RESULTS

Investigations over four decades have shown that harmaline induces rhythmic burst-firing activity in the medial and dorsal accessory inferior olivary nuclei that is transmitted via climbing fibers to Purkinje cells and to the deep cerebellar nuclei, then to brainstem and spinal cord motoneurons. The critical structures required for tremor expression are the inferior olive, climbing fibers, and the deep cerebellar nuclei; Purkinje cells are not required. Enhanced synaptic norepinephrine or blockade of ionic glutamate receptors suppresses tremor, whereas enhanced synaptic serotonin exacerbates tremor. Benzodiazepines and muscimol suppress tremor. Alcohol suppresses harmaline tremor but exacerbates harmaline-associated neural damage. Recent investigations on the mechanism of harmaline tremor have focused on the T-type calcium channel.

DISCUSSION

Like essential tremor, harmaline tremor involves the cerebellum, and classic medications for essential tremor have been found to suppress harmaline tremor, leading to utilization of the harmaline model for preclinical testing of antitremor drugs. Limitations are that the model is acute, unlike essential tremor, and only approximately half of the drugs reported to suppress harmaline tremor are subsequently found to suppress tremor in clinical trials.

Effect of carisbamate on the pharmacokinetics and pharmacodynamics of warfarin in healthy participants

Carisbamate's effect (200 mg twice-daily [study 1], 600 mg twice-daily [study 2]) on warfarin's (25 mg single dose) pharmacokinetics and pharmacodynamics (international normalized ratio) was assessed during 2 open-label studies in healthy participants. Coadministration of either carisbamate regimen produced small changes on the mean maximum plasma concentration (C(max)) and mean area under the plasma concentration-time curve to the last measurable time point (AUC(last)) of (S)- and (R)-warfarin, which are unlikely to be clinically significant. For (S)-warfarin, the ratios (with carisbamate/without carisbamate) of geometric means for C(max) were 105.44 (study 1) and 98.48 (study 2) and for AUC(last) were 109.33 (study 1) and 114.43 (study 2); the corresponding 90% confidence intervals were within the bioequivalence limits of 80% to 125%. Results were similar for (R)-warfarin. Carisbamate at 600 mg (but not 200 mg) twice-daily prolonged the elimination half-life of (S)- and (R)-warfarin by ~10 hours (25% and 32% increase, respectively). Prothrombin time was unaltered by either carisbamate dose. Adverse events with the highest incidence were dizziness (50%) and headache (50%) in study 1 and somnolence (56%) in study 2. Warfarin exposure and international normalized ratio were unaffected by coadministration of carisbamate 200 mg or 600 mg twice-daily. Carisbamate was well tolerated.

Milestones in tremor research

Tremor is one of the most frequent movement disorders and covers a wide spectrum of entities summarized in the 1998 consensus statement of the Movement Disorder Society. Essential tremor and Parkinson tremor are most common and are also the most thoroughly studied. Major progress has occurred in the clinical semiology, neuroimaging, epidemiology, and pathophysiology of tremors. Pathology and genetic research are rapidly growing fields of study. Recently described tremor entities include orthostatic tremor, dystonic tremor, cortical tremor, and thalamic tremor. Treatment research methodology has improved substantially, but few double-blind controlled trials have been published. Deep brain stimulation is the most effective treatment for most tremors but is reserved for advanced cases.

Carisbamate acutely suppresses spasms in a rat model of symptomatic infantile spasms

PURPOSE

Infantile spasms are the signature seizures of West syndrome. The conventional treatments for infantile spasms, such as adrenocorticotropic hormone (ACTH) and vigabatrin, are not always effective, especially in symptomatic infantile spasms (SIS). We tested the efficacy of carisbamate, a novel neurotherapeutic drug, to suppress spasms in the multiple-hit rat model of SIS, and compared it with phenytoin to determine if its effect is via sodium-channel blockade.

METHODS

Sprague-Dawley rats received right intracerebral infusions of doxorubicin and lipopolysaccharide at postnatal day 3 (PN3) and intraperitoneal p-chlorophenylalanine at PN5. A single intraperitoneal injection of carisbamate was administered at PN4, after the onset of spasms, at the following doses: 10 mg/kg (CRS-10), 30 mg/kg (CRS-30), and 60 mg/kg (CRS-60), and was compared to vehicle-injected group (VEH). Video-monitoring of PN6-7 CRS-60 or VEH-injected pups was also done.

KEY FINDINGS

Carisbamate acutely reduced both behavioral spasms (CRS-30 and CRS-60 groups only) and electroclinical spasms during the first 2-3 postinjection hours, without detectable toxicity or mortality. In contrast, phenytoin (20 or 50 mg/kg) failed to suppress spasms.

SIGNIFICANCE

Our findings provide preclinical evidence that carisbamate displays acute anticonvulsive effect on spasms through a sodium channel-independent mechanism. Because spasms in the multiple-hit rat model are refractory to ACTH and transiently sensitive to vigabatrin, carisbamate may constitute a candidate new therapy for SIS, including the ACTH-refractory spasms. Further confirmation with clinical studies is needed.