Computerized Tremor Analysis of Valproate-induced Tremor: A Comparative Study of Controlled-release versus Conventional Valproate

Antiseizure Drugs and Movement Disorders

The relationship between antiseizure drugs and movement disorders is complex and not adequately reviewed so far. Antiseizure drugs as a treatment for tremor and other entities such as myoclonus and restless leg syndrome is the most common scenario, although the scientific evidence supporting their use is variable. However, antiseizure drugs also represent a potential cause of iatrogenic movement disorders, with parkinsonism and tremor the most common disorders. Many other antiseizure drug-induced movement disorders are possible and not always correctly identified. This review was conducted by searching for all the possible combinations between 15 movement disorders (excluding ataxia) and 24 antiseizure drugs. The main objective was to describe the movement disorders treated and worsened or induced by antiseizure drugs. We also summarized the proposed mechanisms and risk factors involved in the complex interaction between antiseizure drugs and movement disorders. Antiseizure drugs mainly used to treat movement disorders are clonazepam, gabapentin, lacosamide, levetiracetam, oxcarbazepine, perampanel, phenobarbital, pregabalin, primidone, topiramate, and zonisamide. Antiseizure drugs that worsen or induce movement disorders are cenobamate, ethosuximide, felbamate, lamotrigine, phenytoin, tiagabine, and vigabatrin. Antiseizure drugs with a variable effect on movement disorders are carbamazepine and valproate while no effect on movement disorders has been reported for brivaracetam, eslicarbazepine, lacosamide, and stiripentol. Although little information is available on the adverse effects or benefits on movement disorders of newer antiseizure drugs (such as brivaracetam, cenobamate, eslicarbazepine, lacosamide, and rufinamide), the evidence collected in this review should guide the choice of antiseizure drugs in patients with concomitant epilepsy and movement disorders. Finally, these notions can lead to a better understanding of the mechanisms involved in the pathophysiology and treatments of movement disorders.

Investigation of the risk of valproic acid-induced tremor: clinical, neuroimaging, and genetic factors

RATIONALE

Investigation of associated risk factors of valproic acid (VPA)-induced tremor helped in increasing tolerance and optimizing treatment scheme individually.

OBJECTIVES

To determine the risk factors of VPA-induced tremor, with particular attention on identifying tremor-susceptible gene mutations.

METHODS

Epileptic patients taking VPA were divided into a tremor and a non-tremor groups. A mutation of rs9652490 in the leucine-rich repeat and immunoglobulin domain-containing Nogo-receptor-interacting protein 1 (LINGO-1) gene was determined by Sanger sequencing. Cerebellar atrophy was assessed, and various cerebellar dimensions were measured on magnetic resonance imaging (MRI) scans.

RESULTS

One hundred and eighty-one of 200 subjects were included. Multivariate regression analysis indicated several VPA-induced tremor-related factors: females (OR = 2.718, p = 0.014), family history of tremor (OR = 7.595, p = 0.003), treatment duration (> 24 months; OR = 3.294, p = 0.002), and daily dosage (> 1,000 mg/d; OR = 19.801, p = 0.008) of VPA. Chi-square tests revealed that treatment with VPA magnesium-ER (p = 0.030) and carbamazepine combination (p = 0.040) reduced the incidence of tremor. One hundred and seventy-six gene sequencing and 86 MRI results excluded any significant difference between the two groups in the mutation of rs9652490 within LINGO-1, the ratio of cerebellar atrophy or the cerebellar-dimension values (p > 0.05). However, mutation of rs9652490 within LINGO-1 was correlated with increased cerebellar atrophy (p = 0.001), reduced cerebellar hemisphere thickness (p = 0.025), and right cerebellar hemisphere longitudinal diameter (p = 0.047).

CONCLUSIONS

Our cohort indicated risk (female, positive family history of tremor, daily dosage > 1000 mg and treatment duration > 24 months of VPA) and protective factors (VPA magnesium-ER and combination with CBZ) of VPA-induced tremor. Mutation of rs9652490 within LINGO-1 correlated with cerebellar atrophy, neither was correlated with VPA-induced tremor.

Clinical and Kinematic Features of Valproate-Induced Tremor and Differences with Essential Tremor

Tremor is a common movement disorder that can be induced by medications, including valproate, which is used for the treatment of epilepsy. However, the clinical and neurophysiological features of valproate-induced tremor are still under-investigated. We performed a clinical and kinematic assessment of valproate-induced tremor by considering tremor body distribution and activation conditions. We investigated possible correlations between demographic and clinical data and kinematic features. Valproate-induced tremor results were also compared with those collected in a large sample of patients with essential tremor. Sixteen valproate-induced tremor patients and 93 essential tremor patients were enrolled. All participants underwent a standardised neurological examination and video recording. Patients also underwent an objective assessment of postural, kinetic and rest tremor of the upper limbs and head tremor through kinematic analysis. Nonparametric tests were used for statistical comparisons between the two groups. Clinical evaluation showed a higher occurrence of rest tremor as well as head or voice, and lower limb involvement in patients with valproate-induced tremor. Kinematic analysis showed a substantial variability in the tremor features of patients with valproate-induced tremor. Compared to essential tremor, we found a higher occurrence of rest tremor of the upper limbs and the involvement of more body segments in valproate-induced tremor patients. Valproate-induced tremor has distinctive clinical and kinematic features, which may suggest that valproate interferes with the cerebellar functions.

Comparison of the relapse rates in seizure-free patients in whom antiepileptic therapy was discontinued and those in whom the therapy was continued: A meta-analysis

About 70% of patients with epilepsy can be seizure-free with an appropriate treatment. When the seizures are under control, discontinuation of the antiepileptic drugs (AEDs) can help avoid their side effects; however, it may increase the risk of relapse. Some studies have compared the relapse rates between patients in whom AEDs have been continued and those in whom AEDs have been discontinued. However, it is not clear whether AED discontinuation causes a higher seizure recurrence rate. This meta-analysis aimed mainly to determine whether the seizure recurrence rate was different between seizure-free patients in whom AEDs were continued and those in whom AEDs were discontinued. The I² value was used for assessing the heterogeneity; the Mantel-Haenszel test was used to calculate the odds ratios (ORs) with 95% confidence intervals (CIs). Seven cohort studies and randomized controlled trials (RCTs) met the inclusion criteria. The study quality evaluation was performed respectively using the Newcastle-Ottawa Scale and the Jadad scale. A total of 1253 patients were included. The relapse rate was higher in patients in whom AEDs were discontinued than in those in whom the AED treatment was continued. Furthermore, we also compared the epilepsy recurrence rates after AED discontinuation between seizure-free patients who were on monotherapy with different AEDs (carbamazepine, phenytoin, sodium valproate, and phenobarbitone/primidone). Four studies and 625 patients were included in this analysis. The epilepsy recurrence rates did not significantly differ between the patients on different AED treatment.

Recent developments in drug-induced movement disorders: a mixed picture

A large and ever-growing number of medications can induce various movement disorders. Drug-induced movement disorders are disabling but are often under-recognised and inappropriately managed. In particular, second generation antipsychotics, like first generation agents, are associated with potentially debilitating side-effects, most notably tardive syndromes and parkinsonism, as well as potentially fatal acute syndromes. Appropriate, evidence-based management is essential as these drugs are being prescribed to a growing population vulnerable to these side-effects, including children and elderly people. Prevention of the development of drug-induced movement disorders is an important consideration when prescribing medications that can induce movement disorders. Recent developments in diagnosis, such as the use of dopamine transporter imaging for drug-induced parkinsonism, and treatment, with the approval of valbenazine and deutetrabenazine, the first drugs indicated for tardive syndromes, have improved outcomes for many patients with drug-induced movement disorders. Future research should focus on development of safer antipsychotics and specific therapies for the different tardive syndromes and the treatment of drug-induced parkinsonism.

The clinical characteristics and related factors of tremor in patients with epilepsy

PURPOSE

Tremor is frequently observed in patients with epilepsy (PWE), which is generally attributed to the side-effect of antiepileptic drugs (AEDs) particularly valproate (VPA) with largely unknown mechanisms. The study aimed to assess the clinical features and related factors of tremor in PWE with tremor.

METHODS

PWE with tremor and a control group of age- and sex-matched PWE without tremor were enrolled. Detailed demographic and clinical information for each individual was recorded. PWE with tremor were evaluated by The Clinical Rating Scale for Tremor (CRST) and Tremor Related Activities of Daily Living (TRADL) questionnaire.

RESULTS

132 individuals were enrolled, which including sixty-six (36 males) PWE with tremor with mean age of 33 years and epilepsy duration of 12.5 years. Tremor was postural in all, with median duration of four and one year from diagnosis and AED treatment to the onset of tremor respectively. The upper limbs were predominantly affected. VPA had been used in 62 (93.9%) PWE with tremor compared to 31 (47.0%) PWE without tremor (P < 0.001). The total CRST score was significantly associated with epilepsy duration and maximum VPA dosage (B = 0.30, p < 0.001; B = 0.32, p = 0.013). Patients with VPA dosage over 17.05 mg/kg/d might be more vulnerable to develop tremor.

CONCLUSIONS

PWE with tremor were more frequently treated with VPA, however, tremor was mild in most without any functional impairment. Epilepsy duration and maximum VPA dosage were important factors of tremor severity, suggesting mechanisms underlying tremor in PWE may be an elaborate interplay of AEDs and disease itself.

Disabling Resting Tremors Induced by the Short-term Infusion of Valproate: A Reversible Phenomenon

Background

Drug-induced tremors after long-term administration of anti-epileptics have been described in the literature. Such tremors are usually postural or action in nature with infrequent resting nature.

Case Report

A 23-year-old female presented in status epilepticus. Past and family histories were negative for seizures. She was managed per protocol with valproate. Within hours, she developed resting tremors. The tremors subsided on changing the anti-epileptic.

Discussion

Resting tremors have mostly been described in the literature as long-term side-effects of valproate. This case illustrates that even short-term infusion of valproate can cause resting tremors.

Insights into Pathophysiology from Medication-induced Tremor

Background

Medication-induced tremor (MIT) is common in clinical practice and there are many medications/drugs that can cause or exacerbate tremors. MIT typically occurs by enhancement of physiological tremor (EPT), but not all drugs cause tremor in this way. In this manuscript, we review how some common examples of MIT have informed us about the pathophysiology of tremor.

Methods

We performed a PubMed literature search for published articles dealing with MIT and attempted to identify articles that especially dealt with the medication's mechanism of inducing tremor.

Results

There is a paucity of literature that deals with the mechanisms of MIT, with most manuscripts only describing the frequency and clinical settings where MIT is observed. That being said, MIT emanates from multiple mechanisms depending on the drug and it often takes an individualized approach to manage MIT in a given patient.

Discussion

MIT has provided some insight into the mechanisms of tremors we see in clinical practice. The exact mechanism of MIT is unknown for most medications that cause tremor, but it is assumed that in most cases physiological tremor is influenced by these medications. Some medications (epinephrine) that cause EPT likely lead to tremor by peripheral mechanisms in the muscle (β-adrenergic agonists), but others may influence the central component (amitriptyline). Other drugs can cause tremor, presumably by blockade of dopamine receptors in the basal ganglia (dopamine-blocking agents), by secondary effects such as causing hyperthyroidism (amiodarone), or by other mechanisms. We will attempt to discuss what is known and unknown about the pathophysiology of the most common MITs.

The clinical features and functional impact of valproate-induced tremor

BACKGROUND

Tremor is a known side-effect of anticonvulsants, particularly of valproate. However, there is a dearth of information regarding detailed clinical features and functional impact of valproate-induced tremor.

METHODS

We studied a cohort of patients treated with anticonvulsants for neurological disorders, through blinded evaluations using the Clinical Rating Scale for Tremor (CRST); we compared the frequency, severity and functional impact of drug-induced tremor between patients treated with valproate and those treated with other anticonvulsants.

RESULTS

From a cohort of 218 consecutive patients, 171 were fully evaluated; 118 patients were taking valproate alone or combined with other anticonvulsants and 53 patients were taking other anticonvulsants. Mean age (±SD) at evaluation of the cohort was 32 ± 13 years, females represented 55.6% of cases. Tremor was more frequently observed in patients taking valproate particularly postural upper limb tremor: 49% vs. 15% (right-side) (P < 0.001) and 48.3% vs. 13.2% (left-side), (P < 0.001); had a higher total CRST score: 12.14 vs. 3.06 (P < 0.001), and required more frequently treatment for drug-induced tremor: 23.7% vs. 5.6% (P=0.005) compared with patients taking other anticonvulsants. Among 118 patients taking valproate, women had a higher total CRST score compared with men: 14.54 ± 14.9 vs. 9.56 ± 9.55 (P=0.034). A weak correlation between the total CRST score, dose per Kg of valproate and serum levels of valproate were observed.

CONCLUSIONS

Tremor is frequently observed in patients taking valproate and is severe enough to require treatment in about 24% of cases.

The relationship between valproate induced tremors and circulating neurotransmitters: a preliminary study

Patients with epilepsy and on valproate (VPA) therapy may develop tremors as a common adverse effect; however, its exact mechanisms are unknown. We hypothesize that VPA-induced tremors may be related to the disturbances in dopamine (DA) and catecholamines (norepinephrine (NE) and epinephrine (E)) concentrations (which are also involved in VPA anticonvulsant effect). We aimed to determine the frequency and type of VPA-induced tremors and their risk factors and to investigate whether or not they are related to the plasma DA, NE and E concentrations. This study included 75 adults with primary epilepsy (mean age: 31.90 ± 5.62 years) and on VPA therapy for 10.57 ± 3.55 years and 40 matched healthy controls. Patients were divided according to the absence or presence of tremors. Blood samples were analyzed for DA, NE and E. Intermittent action tremors in both hands were reported in 31 (41.33%). Chronic standard VPA therapy, older age, longer treatment duration and higher serum concentrations of VPA are risk factors for tremors. None of the patients on controlled release VPA had tremors. Compared to controls, patients (without and with tremors) had lower DA (p = 0.0001) and NE (p = 0.01) concentrations. Compared to patients without tremors, patients with tremors had lower levels DA (p = 0.045) and NE (p = 0.01). Significant correlations were identified between DA with NE (r = 0.540, p = 0.001) concentrations and serum VPA with DA (r = -0.285, p = 0.045) and NE (r = -0.358, p = 0.01) plasma levels. We conclude that benign action tremors are common with standard VPA. Mechanisms underlying VPA-induced tremors may involve abnormalities of DA and NE neurotransmitters.

Seizure outcome in 175 patients with juvenile myoclonic epilepsy--a long-term observational study

INTRODUCTION

Juvenile myoclonic epilepsy (JME) is a genetic generalized epilepsy syndrome. Under appropriate antiepileptic drugs (AED) up to 85% of patients become seizure-free, but many may have a relapse after AED withdrawal.

METHODS

We retrospectively studied 242 patients with JME at the Department of Neurology, Medical University Innsbruck, Austria (1975-2006). We analyzed age at seizure onset, age at last follow up, seizure types, photosensitivity, seizure outcome and neuroimaging findings; inclusion criterion was a medical treatment period of >2 years; exclusion criteria were traumatic or infectious brain injury before the onset of JME and/or gross structural pathology on neuroimaging.

RESULTS

We identified 175 patients (111 women) with a median age at seizure onset of 15 years, (range 3-46) and a median age at follow-up (FU) of 38 years (range 14-87; median FU 8 years, range 2-38). Fourteen percent showed (24/175) photosensitivity on routine EEG. Seizure outcome: 62% (109/175) were seizure-free of myoclonic seizures (MS), generalized tonic clonic seizures (GTCS) and absence seizures (AS) for >1 year, and 53% (94/175) for >2 years, including 16 patients (9%) without AEDs. Thirty-one percent (54/175) were seizure-free between 2 and 5 years, 15% (26/175) between 6 and 10, and 8% (14/175) >10 years; 38% (66/175) were not seizure-free. Not seizure-free patients had more often MS, AS and GTCS within the first year of epilepsy than those who were seizure-free at last FU (11% vs. 3%, Chi(2)=4.679, df=1, p=0.043). Seizure-free patients had more often MS and GTCS as last seizure types in the year before becoming seizure-free (37% vs. 15%, p=0.003), whereas in not seizure-free group MS only and GTCS only persisted.

CONCLUSIONS

JME does not always need lifelong treatment, as a substantial minority of patients remain seizure-free without AEDs. AS, MS and GTCS at onset of the disease are indicators of poor long-term seizure control.

New generation antiepileptic drugs: what do they offer in terms of improved tolerability and safety?

Over the last two decades a total of 11 antiepileptic drugs (AEDs) have been introduced to the US market. Randomized, placebo-controlled trials have yielded information about each drug's efficacy, tolerability, and safety profile; however, few studies have compared the newer generation AEDs directly with the older generation. Comparative studies are not always straightforward in their interpretation, as many characteristics of drugs, both favorable and unfavorable, may not be highlighted by such studies. In general, findings from the literature suggest that the newer generation AEDs (including vigabatrin, felbamate, gabapentin, lamotrigine, tiagabine, topiramate, levetiracetam, oxcarbazepine, zonisamide, pregabalin, rufinamide, and lacosamide) enjoy both improved tolerability and safety compared with older agents such as phenobarbital, phenytoin, carbamazepine, and valproate. This is partially supported by some of the findings of the QSS and the TTA Committee of the American Academy of Neurology (AAN), whose review of four AEDs (gabapentin, lamotrigine, topiramate, and tiagabine) is discussed. Briefly, when compared with carbamazepine, lamotrigine was better tolerated; topiramate adverse events (AEs) were fairly comparable to carbamazepine and valproate; and tiagabine compared with placebo was associated with a higher discontinuation rate due to AEs. The findings of the SANAD trial are also presented; when administered to patients with partial epilepsy, carbamazepine was most likely to fail due to AEs, and lamotrigine and gabapentin were least likely to fail due to AEs. When administered to patients with idiopathic generalized epilepsy, topiramate was most frequently associated with AE-related discontinuation, followed by valproate; and while valproate was the most efficacious drug in this arm of the study, lamotrigine was more tolerable. What makes the SANAD study valuable and somewhat unique is its head-to-head comparison of one drug with another. Such comparative trials are overall lacking for new AEDs, although some conclusions can be drawn from the available data. In the end, however, AED selection must be based on individual patient and drug characteristics.

Lithium and valproate-induced tremors

Lithium and valproate are mood stabilizers known to cause tremor. This article concisely addresses etiological questions, expected time frame of tremor onset, and treatment options for this medication-induced side effect. Along with dosage modifications of the tremor-inducing medication, authors review evidence from small trials of adjunctive treatment modalities.

Once-daily dosing is appropriate for extended-release divalproex over a wide dose range, but not for enteric-coated, delayed-release divalproex: evidence via computer simulations and implications for epilepsy therapy

Divalproex sodium extended-release (divalproex-ER), administered once-daily, maintains plasma valproic acid (VPA) concentrations for 24h, whereas enteric-coated, delayed-release divalproex sodium (divalproex) requires multiple-daily doses to do the same. We hypothesize that a once-daily divalproex regimen should not be administered to epilepsy patients requiring high total daily doses, e.g., 35.6-56 mg/kg/day, due to the potential for high (>125 mg/L) maximum VPA concentrations (C(max)). We examined the impact of once-daily dosing, divalproex vs. divalproex-ER, on steady-state plasma VPA concentration-time profiles at commonly used doses in monotherapy (uninduced) and polytherapy (hepatic enzyme-induced) virtual adult patients. Only the 1125 mg once-daily divalproex dose had mean C(max)<100mg/L; >or=2000 mg produced mean C(max)>or=125 mg/L. Mean divalproex C(min) was approximately 50 mg/L at two of four doses tested, whereas mean ER C(min) was >73 mg/L at all doses tested. Once-daily divalproex peak-trough fluctuation was 4.4-6.2-fold greater than once-daily divalproex-ER. We predict that excursions beyond the conventional recommended VPA plasma concentration range will commonly occur with high total mg daily doses (>or=2000 mg) of enteric-coated divalproex, if dosed once-daily, potentially producing clinical toxicity. This divalproex formulation should not be dosed once-daily at high total mg daily doses due to this risk. Divalproex-ER is the appropriate formulation for administration on a once-daily basis, especially if large total mg/day doses are required for the control of seizure activity.

Postural induced-tremor in psychiatry

Postural tremor is the most common movement disorder in psychiatry, and often a difficult problem for clinicians. It can be classified as physiological, essential, drug-induced, and postural tremor in Parkinson's disease. Drugs used in psychiatry that can produce postural tremor, include lithium, valproic acid, lamotrigine, antidepressants, and neuroleptics. Clinical characteristics of postural tremor induced by each of these drugs are described. Pharmacological strategies for therapy in disabling drug-induced tremor include beta-blockers, primidone, gabapentin, topiramate, and benzodiazepines; their utility, doses and side-effects are also discussed.

Conventional and sustained-release valproate in children with newly diagnosed epilepsy: a randomized and crossover study comparing clinical effects, patient preference and pharmacokinetics

OBJECTIVE

It has been suggested that sustained-release valproate (VPA) formulations may be more effective and better tolerated than conventional VPA due to better compliance and lower fluctuations in VPA serum concentrations, but comparative trials with conventional VPA in children are scarce. This randomized and crossover trial compared the efficacy (complete control of seizures), the tolerability, and the patient (or parents) preference of conventional VPA twice daily (CVbid) with those of sustained-release chrono VPA twice daily (ChVbid), once daily in the morning (ChVom) or once daily in the evening (ChVoe) in monotherapy.

METHODS

The study was carried out in 48 children (29 girls), aged 5-14 years, with newly diagnosed partial epilepsy (n=26), or idiopathic generalized epilepsy (n=22). The study duration was 16 months (four phases of 4 months each). VPA pharmacokinetics data were also compared in the different regimens. Mean VPA dosage was of approximately 870 mg/day (approximately 22 mg/kg/day) and mean VPA concentration was of approximately 89 mg/l at 12 h post-dose and of 54 mg/l at 24 h post-dose.

RESULTS

By intention in treatment there were no significant differences in efficacy (73%, 83%, 77% and 75%, respectively) or in adverse reaction frequency (56%, 58%, 67% and 46%, respectively). There were significant differences, however, in patient (or parents) preference, the order being ChVoe (31%) > ChVom (25%) > CVbid (17%) > ChVbid (8%). The mean VPA serum concentration fluctuation between 4 h and 0 h post-morning-dose was nonsignificantly lower after CVbid than after ChVbid. Fluctuation was significantly higher after ChVom than after CVbid or ChVbid. The mean VPA serum concentration difference between 12 h and 24 h post-dose was approximately 40 mg/l.

CONCLUSION

Although our results should be confirmed by a larger study, they suggest that the efficacy and tolerability of chrono valproate is similar to that of conventional valproate, and that the main advantage is the once-daily administration.

Safety and tolerability of mood-stabilising anticonvulsants in the elderly

The authors review current research on the safety and tolerability of anticonvulsant medications used for individuals over the age of 60 years with affective disorders, agitation and other psychiatric disorders. Three anticonvulsants currently approved in the US for treatment of bipolar affective disorder are reviewed: valproate, lamotrigine and extended-release carbamazepine. The authors discuss the pharmacokinetics, pharmacodynamics, drug-drug interactions and the impact of ageing for each drug. There are few studies of anticonvulsant medications in elderly patients with bipolar disorder or other psychiatric conditions. Therefore, the authors summarise adverse events of greatest prevalence and/or greatest severity based on data derived predominately from studies of geriatric patients with epilepsy and/or other non-psychiatric indications. Guidelines are offered for the safe use of these medications in the elderly, based on research literature.

Drug-induced tremors

Tremor is a common complaint for many patients. Caffeine and beta-adrenergic agonists are well-recognised drugs that cause or exacerbate tremors. Other tremorogenic drugs, such as selective serotonin reuptake inhibitors and tricyclic antidepressants, are less well recognised. Recognition of the drugs that can cause or exacerbate tremors can help prompt diagnosis, avoids unnecessary tests, and allows clinicians to quickly take corrective action (usually by discontinuing the tremor-inducing drugs). The aim of this review is to provide clinicians with current information on drugs that are associated with tremor and the correct treatment of these drug-induced tremors.