Long-term maintenance treatment of restless legs syndrome with gabapentin enacarbil: a randomized controlled study

Rethinking clinical trials in restless legs syndrome: A roadmap

The number of large clinical trials of restless legs syndrome (RLS) have decreased in recent years, this coincides with reduced interest in developing and testing novel pharmaceuticals. Therefore, the International Restless Legs Syndrome Study Group (IRLSSG) formed a task force of global experts to examine the causes of these trends and make recommendations to facilitate new clinical trials. In our article, we delve into potential complications linked to the diagnostic definition of RLS, identify subpopulations necessitating more attention, and highlight issues pertaining to endpoints and study frameworks. In particular, we recommend developing alternative scoring methods for more accurate RLS diagnosis, thereby improving clinical trial specificity. Furthermore, enhancing the precision of endpoints will increase study effect sizes and mitigate study costs. Suggestions to achieve this include developing online, real-time sleep diaries with high-frequency sampling of nightly sleep latency and the use of PLMs as surrogate markers. Furthermore, to reduce the placebo response, strategies should be adopted that include placebo run-in periods. As RLS is frequently a chronic condition, priority should be given to long-term studies, using a randomized, placebo-controlled, withdrawal design. Lastly, new populations should be investigated to develop targeted treatments such as mild RLS, pregnancy, hemodialysis, or iron-deficient anemia.

Current and emerging pharmaceutical strategies for the treatment and management of restless legs syndrome

INTRODUCTION

Restless legs syndrome (RLS) is a sensory-motor sleep disorder that affects up to 13% of adults in the Western world and 2-4% of children. It impairs night sleep with an impact on daily performances and life quality. Thus, moderate-to-severe RLS requires pharmacological treatment.

AREAS COVERED

In the present review, which is based on PubMed searches with no time limits, the authors discuss the recommended pharmacotherapy for RLS in addition to other emerging treatment options. The authors provide coverage to the current recommendations for both adults and pediatric patients with RLS.

EXPERT OPINION

Current evidence suggests removing all causes of secondary RLS, including iron deficiency, chronic renal failure, drugs, and treating other sleep disorders that may worsen symptoms. Also, intermittent RLS should be addressed with behavioral measures and on-demand therapy. For chronic persistent RLS, α2δ calcium channel ligands are a first-line pharmacological approach, whereas dopamine agonists are associated with increased risk and should be spared. When RLS is refractory to first-line treatment, polytherapy, or opioid monotherapy should be considered. Nonetheless, some patients may not reach sustained symptom relief. Further research is needed to better understand the pathophysiology of RLS and to develop newer more effective drugs.

How effective are treatment guidelines for augmented RLS?

Study Objectives

The objective of this study was to assess the effectiveness of current treatment guidelines for restless legs syndrome (RLS) augmentation in patients on dopamine agonists (DAs) which recommend a cross-titration strategy to an alpha-2-delta ligand (A2D) and/or opioid.

Methods

Consecutive new consultations for RLS with both augmentation and active treatment with DAs at the time of initial assessment were included if followed >5 months. Clinical information from the semi-structured initial consultation, and subsequent visits until their most recent/final visit was extracted. Clinical Global Impression-Severity (CGI-S) and Clinical Global Impression-Improvement (CGI-I) scores were retrospectively determined by two independent evaluators.

Results

In the 63 patients with augmented RLS on DAs, followed for 5–59 months (mean = 28, SD = 14), the average age was 67.6 (SD = 9.8) and 63% were female. Mean duration of prior dopaminergic therapy was 11.6 years (SD = 6.7) and average pramipexole equivalent dose was 1.23 mg (SD = 1.22 mg). At baseline, RLS was “moderate-markedly” severe (CGI-S = 4.9). At the final/most recent visit, 78% (49/63) were classified as Responders (CGI-I ≤ 2, “Much” or “Very Much Improved”) with an average CGI-S of 2.4 (“borderline-mildly ill”). Responders (59%) were more likely to have discontinued DAs than Non-Responders (40%), and mean opioid doses were higher in Responders (39 vs 20 MME). No differences in baseline DA dose, final A2D dose, or iron therapy were observed between groups. Responders did have significantly more severe RLS, more sleep maintenance insomnia, and greater subjective daytime sleepiness at baseline (p < 0.05).

Conclusions

Guideline-based management is effective in most patients with augmented RLS on DAs.

Restless leg syndrome presenting as chronic severe limb pain in a dialysis patient

"Chronic pain" is a commonly reported symptom among hemodialysis patients. Despite its high prevalence and the poor health-related quality of life associated with it, chronic pain remains an ineffectively assessed and managed entity in dialysis patients. We report a case of a 55-year-old gentleman on maintenance hemodialysis who presented with 3 months history of "excruciating flitting and fleeting type" of pain largely involving both lower limbs and occasionally neck, shoulder, chest, and upper limbs. The pain was so intolerable that it even triggered suicidal intentions in the patient. Common causes of chronic pain in dialysis patients were considered, but the initial history and clinical examination remained elusive. The patient was empirically started on oral analgesics, benzodiazepines, calcitriol, and levocarnitine supplementation but had no significant effect on his symptoms. A comprehensive repeat clinical history revealed the nocturnal periodicity of symptoms, specific aggravation of pain with inactivity, and its temporary relief with movement. This helped us narrow down the diagnosis to restless leg syndrome (RLS) amidst the myriad causes of chronic pain in dialysis patients. The "constant urge to move the legs" which is the defining characteristic of RLS was inconspicuous in our patient and excruciating pain was the predominant manifestation. This atypical presentation of RLS with agonizing pain involving multiple sites of the body led to a delay in the diagnosis and initiation of appropriate therapeutic measures. The patient had a dramatic response to therapy with dopamine agonists and withdrawal of the drug led to reappearance of his symptoms which further confirmed the diagnosis of RLS. RLS should be considered in the evaluation of chronic pain in dialysis patients and renal health care providers should familiarize themselves with the varied atypical, forme fruste manifestations of RLS to avoid diagnostic delay of this disabling but treatable condition.

[Restless legs syndrome]

Restless legs syndrome (RLS) is seen widely in clinical practice. RLS commonly occurs at night time and presents with unpleasant or uncomfortable sensations in the legs that causes an urge to move them. This article describes the epidemiology, risk factors and pathophysiology of RLS. There is a detailed description of clinical presentations, diagnostic criteria and also management of RLS.

Pharmacologic Treatment of Restless Legs Syndrome

Restless legs syndrome (RLS)/Willis-Ekbom disease is a neurologic disorder characterized by a strong desire to move when at rest (usually in the evening) and paraesthesia in their lower legs. The most widely used therapies for first-line treatment of RLS are dopaminergic drugs; however, their long-term use can lead to augmentation. α2δ Ligands, opioids, iron, glutamatergic drugs, adenosine, and sleep aids have been investigated as alternatives. The pathogenesis of RLS is not well understood. Despite the efficacy of dopaminergic drugs in the treatment of this disorder, unlike in Parkinson's disease dopaminergic cell loss in the substantia nigra has not been observed in RLS. The etiology of RLS is likely complex, involving multiple neural pathways. RLS-related genes identified in genome-wide association studies can provide insight into the mechanistic basis and pathophysiology of RLS. Here we review the current treatments and knowledge of the mechanisms underlying RLS.

Emerging Concepts of the Pathophysiology and Adverse Outcomes of Restless Legs Syndrome

Restless legs syndrome (RLS), also known as Willis-Ekbom disease (WED), is a common neurological disorder affecting up to 5% to 10% of the population, but it remains an underdiagnosed condition. RLS/WED is characterized by uncomfortable sensations, mainly in the legs, which appear during inactivity and worsen in the evening or at night. The prevalence of RLS/WED and periodic leg movements (PLMs) is increased in patients with sleep-disordered breathing, particularly in those with OSA, the most common sleep disorder encountered in sleep centers. New advances in the pathophysiology of RLS/WED have shown important implications for various genetic markers, neurotransmitter dysfunction, and iron deficiency. A practical approach to RLS/WED management includes an accurate diagnosis, the identification of reversible contributing factors, and the use of nonpharmacological therapies, including iron substitution (oral or IV) therapy. Many pharmacological agents are effective for the treatment of RLS/WED. Until recently, the first-line treatment of RLS/WED consisted of low-dose dopamine agonists (DA). However, given the fact that DAs cause high rates of augmentation of symptoms, international guidelines recommend that whenever possible the initial treatment of choice should be an α2δ ligand, and avoidance of dopaminergic agents unless absolutely necessary. If necessary, the lowest effective dose should be used for only the shortest possible time. The symptoms of RLS/WED can disrupt the quality of sleep as well as the quality of life. IV iron therapy may be considered in patients with refractory RLS. A better understanding of RLS/WED pathophysiology will allow patients to receive tailored therapy, resulting in an improved quality of life.

Use of α2δ Ligands for Restless Legs Syndrome/Willis Ekbom Disease

Restless legs syndrome is a common neurological condition affecting a substantial portion of the population. It can be an idiopathic disorder, or one that is secondary to another cause. Given that the underlying pathophysiology of restless legs syndrome is not well understood, several drug classes have been studied for symptom control. While dopamine agonists have long been the mainstay of first-line treatment for restless legs syndrome, recently, the α2δ ligands have been increasingly used. These agents have proven both efficacious and safe in a number of clinical trials. Additionally, compared with the dopamine agonists, they have been associated with less augmentation, a phenomenon whereby symptoms emerge earlier in the day, become more severe, and may spread to areas of the body previously unaffected. Newer clinical guidelines for restless legs syndrome are increasingly recommending the α2δ ligands as a logical first-choice medication for patients needing drug therapy for symptom control.

Pharmacological Management of Restless Legs Syndrome and Periodic Limb Movement Disorder in Children

Restless legs syndrome (RLS) and periodic limb movement disorder (PLMD) are under-recognized sleep disorders in children and adolescents. Several recent epidemiological studies have shown that RLS and PLMD are common in the pediatric population, and if left untreated, may lead to cardiovascular and neurocognitive consequences. Therefore, early diagnosis and intervention may help preventing long-term consequences. The management of RLS and PLMD in children involves both non-pharmacologic and pharmacologic approaches. Although there is emerging literature supporting medical therapy in children with RLS and PLMD, the overall experiences with these medications remain limited. Most children and adolescents with RLS and PLMD have low iron storage; therefore, iron therapy should be considered as the first line of treatment in children. Currently, there is no FDA-approved medication for RLS and PLMD in children. There is increasing evidence on the effectiveness of dopaminergic medications in children but the data are quite limited. Other medications such as α2δ-1 ligands, benzodiazepine, and clonidine are frequently used, but have not been adequately investigated in children. Further studies are needed to evaluate the safety and efficacy of pharmacologic therapy for RLS and PLMD in children.

Efficacy and Tolerability of Gabapentin in Adults with Sleep Disturbance in Medical Illness: A Systematic Review and Meta-analysis

BACKGROUND AND PURPOSE

The aim of this study was to systematically review the efficacy and tolerability of gabapentin in the treatment of sleep disturbance in patients with medical illness.

METHODS

PubMed was searched for randomized, double-blinded, placebo-controlled trials that reported sleep changes during gabapentin treatment up to November 2015.

FINDINGS

This review included 26 studies involving 4,684 participants. Except for Composite Endpoint 3 [standardized mean difference (SMD) = 0.09, 95% confidence interval (CI): -0.05-0.22] compared with the placebo group, the gabapentin group showed superior outcomes on our endpoints: Composite Endpoint 1 (SMD = 0.50, 95% CI: 0.28-0.71), Composite Endpoint 2 (SMD = -0.53, 95% CI: -0.77 to -0.30), Composite Endpoint 4 (SMD = -0.38, 95% CI: -0.58 to -0.19), Composite Endpoint 5 [risk ratio (RR) = 1.79, 95% CI: 1.24-2.58], and Composite Endpoint 6 (RR = 0.48, 95% CI: 0.32-0.72). However, the patients in the gabapentin group showed worse tolerance than those in the placebo group (RR = 1.38, 95% CI: 1.08-1.76).

IMPLICATIONS

This study is the first to systematically assess the clinical value of gabapentin for the treatment of sleep disorders. We found that regardless the type of sleep outcomes, gabapentin displayed stable treatment efficacy for sleep disturbance in patients with medical illness. However, when an average dose of approximately 1,800 mg/day was used, the risk of treatment discontinuation or drug withdrawal was relatively high. We recommend that further studies confirm these findings in patients with primary sleep disorders.

Gabapentin Enacarbil: A Review in Restless Legs Syndrome

Gabapentin enacarbil is an extended-release prodrug of gabapentin that is approved in the USA (Horizant(®)) and Japan (Regnite(®)) for the treatment of moderate to severe primary restless legs syndrome (RLS) in adults [featured indication]. This article summarizes pharmacological, efficacy and tolerability data relevant to the use of oral gabapentin enacarbil in this indication. In double-blind, multicentre trials, treatment with gabapentin enacarbil 600 mg/day for 12 weeks significantly improved the symptoms of moderate to severe primary RLS in adults. Gabapentin enacarbil also significantly improved RLS pain scores and generally improved sleep and mood outcomes. These data are supported by retrospective pooled analyses of three of these trials (XP081, PIVOT RLS I and PIVOT RLS II), with gabapentin enacarbil generally improving symptoms irrespective of disease severity, associated sleep disturbance or prior dopamine agonist use. Responses to gabapentin enacarbil were sustained in longer-term trials, with lower relapse rates in gabapentin enacarbil than placebo recipients in a longer-term maintenance study. Overall, in short and longer-term trials, relatively few patients discontinued treatment, adverse events were mostly mild to moderate in severity, and somnolence/sedation and dizziness were the most commonly reported adverse events. Notably, there were no reports of augmentation or QT-interval prolongation. Gabapentin enacarbil is an important agent for the treatment of adults with moderate to severe primary RLS.

Restless Legs Syndrome in Patients With Chronic Kidney Disease

Symptoms of restless legs syndrome (RLS) are common in patients with chronic kidney disease (CKD) on dialysis; symptoms of RLS are estimated to affect up to 25% of patients on dialysis when the international RLS diagnostic criteria are applied. RLS is a neurologic disorder with a circadian rhythmicity characterized by an overwhelming urge to move the legs during rest, which can be relieved temporarily by movement. RLS has been associated with an increase in sleep disturbance, higher cardiovascular morbidity, decreased quality of life, and an increased risk of death in patients with CKD. Although the exact pathophysiology of RLS is unknown, it is thought to involve an imbalance in iron metabolism and dopamine neurotransmission in the brain. The symptoms of moderate to severe RLS can be treated with several pharmacologic agents; however, data specific to patients on dialysis with RLS are lacking. The purpose of this article is to examine the relationship between, and complications of, RLS and CKD both in dialysis and nondialysis patients, and discuss the treatment options for patients on dialysis with RLS.

The Effect of Gabapentin Enacarbil on Pain Associated with Moderate-to-Severe Primary Restless Legs Syndrome in Adults: Pooled Analyses from Three Randomized Controlled Trials

BACKGROUND

Adults with moderate-to-severe primary restless legs syndrome (RLS) often experience painful dysesthesias, which may lead to impaired quality of life.

OBJECTIVES

The aim of this study was to assess the effects of gabapentin enacarbil (GEn) on pain associated with moderate-to-severe primary RLS in adults.

METHODS

Data were pooled from three double-blind, randomized, placebo-controlled, 12-week trials (NCT00298623, NCT00365352, NCT01332305) for adults receiving GEn or placebo once daily. Change in average daily RLS pain score and a combined International Restless Legs Scale (IRLS)-pain response were examined.

RESULTS

The modified intention-to-treat population included 671 adults (placebo, n = 244; GEn 600 mg, n = 161; GEn 1200 mg, n = 266). Both GEn doses significantly improved average daily RLS pain score at week 12 (p < 0.001 for GEn 600 mg vs. placebo and GEn 1200 mg vs. placebo). The combined IRLS-pain response subanalysis included 366 patients with a baseline IRLS total score ≥15 and pain score ≥4 (placebo, n = 133; GEn 600 mg, n = 86; GEn 1200 mg, n = 147). Most patients were both IRLS and pain responders (placebo, 40 %; GEn 600 mg, 70 %; GEn 1200 mg, 67 %). Spearman rank correlations between IRLS total and pain score (change from baseline to week 12) were moderate or strong. The most frequent treatment-emergent adverse events were somnolence (placebo, 5 %; GEn 600 mg, 20 %; GEn 1200 mg, 23 %) and dizziness (placebo, 4 %; GEn 600 mg, 13 %; GEn 1200 mg, 22 %).

CONCLUSIONS

This post hoc pooled analysis suggests that GEn (600 and 1200 mg) once daily significantly improved pain associated with moderate-to-severe primary RLS in adults; however, the analysis was not powered to detect statistical differences between the two GEn doses. Numerically, more GEn-treated patients had a combined IRLS-pain response than placebo-treated patients.

Incidence of Augmentation in Primary Restless Legs Syndrome Patients May Not Be That High: Evidence From A Systematic Review and Meta-Analysis

Augmentation is a common complication of primary restless legs syndrome (RLS) during treatment; however, its incidence rate remains unclear.The aim of this study is investigate the rate of augmentation during RLS treatment.We searched 6 databases, including PubMed, OVID, Embase, Wiley citations, Web of Science research platform (including SciELO Citation Index, Medline, KCI Korean Journal Database, the Web of Science™ Core Collection), and the Cochrane library, and screened the reference lists of the included trials and recently published reviews.Randomized controlled trials and observational studies that reported augmentation events during RLS treatment.Primary RLS patients older than 18 years.No restrictions regarding intervention types were applied.Three investigators independently extracted and pooled the data to analyze the augmentation rate of the total sample and of patient subgroups with different interventions, treatment durations and drug regimens and different geographic origins. Fixed-effects or random-effects model was used for pooled analysis.A total of 60 studies involving 11,543 participants suggested an overall augmentation rate of 5.6% (95% confidence intervals (CI), 4.0-7.7). The augmentation incidence was 6.1% (95% CI, 4.1-9.1) for long-term treatment and 3.3% (95% CI, 1.4-7.3) for short-term treatment. In addition, 27.1% (95% CI, 12.3-49.5) of the levodopa-treated patients, 6.0% (95% CI, 4.1-8.8) of the patients treated with dopamine agonists, and 0.9% (95% CI, 0.2-3.3) of the patients taking pregabalin or gabapentin developed augmentation. Augmentation occurred in 7.2% (95% CI, 5.0-10.3) of the patients taking immediate-release drugs and in 1.7% (95% CI, 0.6-5.0) of the patients taking transdermal application.The main limitations are that the augmentation rates were not evaluated according to drug dosage, gender, and age and symptom severity.Approximately 5 to 6 in 100 RLS patients developed augmentation during treatment.

Treatment response to sleep, pain, and mood disturbance and their correlation with sleep disturbance in adult patients with moderate-to-severe primary restless legs syndrome: Pooled analyses from 3 trials of gabapentin enacarbil

INTRODUCTION

This pooled analysis investigated the effects of gabapentin enacarbil (GEn) on clinical correlates of sleep disturbance in adults with moderate-to-severe primary restless legs syndrome (RLS) and no-to-moderate or severe-to-very severe baseline sleep disturbance.

METHODS

Co-primary end-points were mean change from baseline to week 12 in International Restless Legs Scale (IRLS) total score and proportion of responders ('much'/'very much' improved) on the investigator-rated Clinical Global Impression-Improvement (CGI-I) scale (week 12). Pain, mood, individual IRLS items, and safety were assessed.

RESULTS

The modified intent-to-treat population was 671 adults randomized to GEn 600 mg (n = 161), GEn 1200 mg (n = 266), or placebo (n = 244). GEn significantly improved least squares mean change in IRLS total score from baseline versus placebo for no-to-moderate (GEn 600 mg,- 12.3; 1200 mg, - 11.3; placebo, - 7.7) and severe-to-very severe (- 16.6; - 17.0; - 12.7) groups (all P < 0.01). Significantly more GEn-treated patients (both doses) were CGI-I responders (week 12) versus placebo in both sleep subgroups (all P < 0.01). GEn substantially improved mood and pain scores for both sleep subgroups versus placebo. The most frequent treatment-emergent adverse events were somnolence and dizziness.

CONCLUSION

GEn (600 mg and 1200 mg) was effective and well tolerated in adults with moderate-to-severe primary RLS regardless of baseline sleep disturbance level.

Restless legs syndrome: clinical presentation diagnosis and treatment

Restless legs syndrome (RLS) is a circadian disorder of sensory-motor integration that may be related to genetically determined dysregulation of iron transport across the blood-brain barrier. Dopamine agonists (DAs) have been considered the first-line therapy, but with the growing appreciation of problems associated with long-term treatment, particularly augmentation and impulse control disorder, alpha-2-delta drugs, such as gabapentin, are now considered the first line of treatment in patients with troublesome RLS. Opioids can be considered as an alternative therapy, particularly in patients with DA-related augmentation. In more severe cases, a combination therapy may be required. Intravenous iron therapy may be considered on those patients with refractory RLS.

The long-term treatment of restless legs syndrome/Willis-Ekbom disease: evidence-based guidelines and clinical consensus best practice guidance: a report from the International Restless Legs Syndrome Study Group

A Task Force was established by the International Restless Legs Syndrome Study Group (IRLSSG) to develop evidence-based and consensus-based recommendations for the long-term pharmacologic treatment of restless legs syndrome/Willis-Ekbom disease (RLS/WED). The Task Force reviewed the results of all studies of RLS/WED treatments with durations of 6 months or longer presented at meetings over the past 2 years, posted on Web sites of pharmaceutical companies, or published in peer-reviewed journals, asking the questions, "What is the efficacy of this treatment in patients with RLS/WED?" and "What is the safety of this treatment in patients with RLS/WED?" The Task Force developed guidelines based on their review of 61 papers meeting inclusion criteria, and using a modified evidence-grading scheme. Pregabalin has been established as effective for up to 1 year in treating RLS/WED (Level A evidence). Pramipexole, ropinirole, and rotigotine have been established as effective for up to 6 months in treating RLS/WED (Level A). The following drugs have been established as probably effective (Level B) in treating RLS/WED for durations ranging from 1 to 5 years: gabapentin enacarbil, pramipexole, and ropinirole (1 year); levodopa (2 years); and rotigotine (5 years). Because of associated safety concerns, pergolide and cabergoline should not be used in the treatment of RLS/WED unless the benefits clearly outweigh the risks. Other pharmacologic therapies have insufficient evidence to support their long-term use in treating RLS/WED. The IRLSSG Task Force also developed consensus-based strategies for the prevention and treatment of complications (such as augmentation, loss of efficacy, excessive daytime sleepiness, and impulse control disorders) that may develop with the long-term pharmacologic treatment of RLS/WED. The use of either a dopamine-receptor agonist or α2δ calcium-channel ligand is recommended as the first-line treatment of RLS/WED for most patients, with the choice of agent dependent on the patient's severity of RLS/WED symptoms, cognitive status, history, and comorbid conditions.

Gabapentin enacarbil for the treatment of moderate to severe primary restless legs syndrome (Willis-Ekbom disease): 600 or 1,200 mg dose?

Gabapentin enacarbil is a prodrug of the anticonvulsant gabapentin. The efficacy and safety of gabapentin enacarbil for the treatment of moderate to severe primary restless legs syndrome (RLS) has been evaluated in several clinical trials in the United States and Japan. Although most clinical trials assessed gabapentin enacarbil at doses greater than 600 mg/day and demonstrated the overall safety and efficacy (defined as improvements in the coprimary endpoints of the international RLS rating scale [IRLS] total score and Clinical Global Impression-Improvement response), the US Food and Drug Administration approved the 600 mg once-daily dosage because doses higher than 600 mg/day were considered to provide no additional benefits and were associated with higher rates of adverse events, such as somnolence and dizziness. Nonetheless, the results of clinical trials and post hoc meta-analyses have indicated that the 1,200 mg once-daily dosage was the most validated gabapentin enacarbil treatment for not only subjective RLS symptoms but also severe sleep disturbance associated with RLS. A Japanese dose-finding study showed that 900 mg/day, the intermediate dose between 600 and 1,200 mg, failed to show a significant improvement in IRLS total score, probably because many of the patients who discontinued treatment did so early, suggesting that a half-landing dose may cause more adverse effects than favorable ones in some RLS patients early in the treatment. Gabapentin enacarbil may have two distinct therapeutic doses for the treatment of RLS: 600 mg/day or lower doses for the treatment of subjective RLS symptoms and 1,200 mg/day or higher doses for the treatment of both subjective RLS symptoms and associated problems such as severe sleep disturbances.

Treatment of restless legs syndrome

Restless legs syndrome (RLS) is a common disorder diagnosed by the clinical characteristics of restlessness in the legs associated often with abnormal sensations that start at rest and are improved by activity, occurring with a diurnal pattern of worsened symptoms at night and improvement in the morning. RLS is the cause of impaired quality of life in those more severely afflicted. Treatment of RLS has undergone considerable change over the last few years. Several classes of medications have demonstrated efficacy, including the dopaminergic agents and the alpha-2-delta ligands. Levodopa was the first dopaminergic agent found to be successful. However, chronic use of levodopa is frequently associated with augmentation that is defined as an earlier occurrence of symptoms frequently associated with worsening severity and sometimes spread to other body areas. The direct dopamine agonists, including ropinirole, pramipexole, and rotigotine patch, are also effective, although side effects, including daytime sleepiness, impulse control disorders, and augmentation, may limit usefulness. The alpha-2-delta ligands, including gabapentin, gabapentin enacarbil, and pregabalin, are effective for RLS without known occurrence of augmentation or impulse control disorders, although sedation and dizziness can occur. Other agents, including the opioids and clonazepam do not have sufficient evidence to recommend them as treatment for RLS, although in an individual patient, they may provide benefit.

Randomized, placebo-controlled pilot trial of gabapentin during an outpatient, buprenorphine-assisted detoxification procedure

This pilot study examined the efficacy of the N-type calcium channel blocker gabapentin to improve outcomes during a brief detoxification protocol with buprenorphine. Treatment-seeking opioid-dependent individuals were enrolled in a 5-week, double-blind, placebo-controlled trial examining the effects of gabapentin during a 10-day outpatient detoxification from buprenorphine. Participants were inducted onto buprenorphine sublingual tablets during Week 1, were randomized and inducted onto gabapentin or placebo during Week 2, underwent a 10-day buprenorphine taper during Weeks 3 and 4, and then were tapered off gabapentin/placebo during Week 5. Assessments included thrice-weekly opioid withdrawal scales, vitals, and urine drug screens. Twenty-four individuals (13 male; 17 Caucasian, 3 African American, 4 Latino; mean age 29.7 years) participated in the detoxification portion of the study (gabapentin, n = 11; placebo, n = 13). Baseline characteristics did not differ significantly between groups. Self-reported and observer-rated opioid withdrawal ratings were relatively low and did not differ between groups during the buprenorphine taper. Urine results showed a Drug × Time interaction, such that the probability of opioid-positive urines significantly decreased over time in the gabapentin versus placebo groups during Weeks 3 and 4 (OR = 0.73, p = .004). These results suggest that gabapentin reduces opioid use during a 10-day buprenorphine detoxification procedure.

Gabapentin enacarbil in Japanese patients with restless legs syndrome: a 12-week, randomized, double-blind, placebo-controlled, parallel-group study

OBJECTIVE

Gabapentin enacarbil (GEn) was effective and well-tolerated for the treatment of restless legs syndrome (RLS) in North American studies. However, no placebo-controlled studies of GEn have been performed in Asian patients with RLS. Therefore, we investigated the efficacy and safety of GEn in Japanese patients with RLS to determine the optimal dosage.

RESEARCH DESIGN AND METHODS

Outpatients with RLS (International Restless Legs Syndrome Rating Scale (IRLS) scores ≥15) were randomized (n = 474) and treated (n = 469) in a double-blind manner with once-daily placebo (n = 116), 600 (n = 120), 900 (n = 119) or 1200 (n = 114) mg GEn for 12 weeks.

CLINICAL TRIAL REGISTRATION

NCT00530530 (ClinicalTrials.gov)

MAIN OUTCOME MEASURE

The primary outcome was the change in IRLS score. Secondary outcomes included Investigator (ICGI)- and Patient (PCGI)-rated Clinical Global Impression and adverse events.

RESULTS

The mean change in IRLS score from baseline to the final observation was -8.96 for placebo versus -11.10, -10.28 and -11.38 for 600, 900 and 1200 mg GEn. Williams' multiple comparison test showed that only 1200 mg GEn was superior to placebo (p = 0.011). However, in post hoc mixed-effects models with repeated measures, which accounted for the time-course of changes in IRLS, the placebo-adjusted changes were -2.31, -1.92 and -2.31 for 600, 900 and 1200 mg GEn. ICGI and PCGI response rates were significantly greater for all three GEn doses versus placebo (all p ≤ 0.014). Adverse events, including somnolence, dizziness and nasopharyngitis, were frequent but of mild-to-moderate severity. However, there was a tendency toward a dose-dependent increase in the incidence of adverse events.

CONCLUSIONS

GEn is effective and well-tolerated for the treatment of RLS in Japanese patients. All three doses produced improvements in IRLS compared with placebo; 600 mg GEn is a suitable target dose. However, our analysis possibly introduced positive bias by assuming that symptoms improve after discontinuation.

Treatment of dyssomnias and parasomnias in childhood

OPINION STATEMENT

Dyssomnias are sleep disorders associated with complaints of insomnia or hypersomnia. The daytime sleepiness of narcolepsy is treated by a combination of planned daytime naps, regular exercise medications such as modafinil, or salts of methylphenidate, or amphetamine. Cataplexy that accompanies narcolepsy is treated with anticholinergic agents, selective serotonin reuptake inhibitors, or sodium oxybate. Children with neurodevelopmental disabilities such as autism have sleep initiation and maintenance difficulties on a multifactorial basis, with favorable response to melatonin in some patients. Childhood onset restless legs syndrome is often familial, associated with systemic iron deficiency, and responsive to iron supplementation and gabapentin. Parasomnias are episodic phenomena events which occur at the sleep -- wake transition or by intrusion on to sleep. Arousal parasomnias such as confusional arousals and sleep walking can sometimes be confused with seizures. A scheme for differentiating arousal parasomnias from nocturnal seizures is provided. Since arousal parasomnias are often triggered by sleep apnea, restless legs syndrome, or acid reflux, treatment measures directed specifically at these disorders often helps in resolution. Clonazepam provided in a low dose at bedtime can also alleviate sleep walking and confusional arousals. Obstructive sleep apnea affects about 2 percent of children. Adeno-tonsillar hypertrophy, cranio-facial anomalies, and obesity are common predisposing factors. Mild obstructive sleep apnea can be treated using a combination of nasal corticosteroids and a leukotriene antagonist. Moderate to severe obstructive sleep apnea are treated with adeno-tonsillectomy, positive airway pressure breathing devices, or weight reduction as indicated. This paper provides an overview of the topic, with an emphasis on management steps. Where possible, the level of evidence for treatment recommendations is indicated.

Gabapentin enacarbil: in patients with restless legs syndrome

Oral gabapentin enacarbil is approved in adult patients for the treatment of moderate to severe primary restless legs syndrome (RLS) [featured indication] and the management of postherpetic neuralgia. In the 12-week Patient Improvements in Vital Outcomes following Treatment (PIVOT) RLS I and II trials in adult patients with moderate to severe primary RLS (n > 500 total evaluable), once-daily gabapentin enacarbil 600 or 1,200 mg significantly improved mean International Restless Legs Scale (IRLS) total scores compared with placebo, with significantly higher investigator-rated Clinical Global Impression-Improvement (CGI-I) responder rates in gabapentin enacarbil groups than in placebo groups. Improvements in other sleep outcomes (assessed using various scales) also generally favoured gabapentin enacarbil treatment. These data are supported by results from a polysomnography, crossover (two 4-week treatment periods) trial (n > 100 evaluable). Improvements in RLS symptoms with gabapentin enacarbil were maintained in a 52-week extension study of clinical trials, including PIVOT RLS I and II. The longer-term efficacy of gabapentin enacarbil in patients with moderate to severe RLS was also demonstrated in the 36-week PIVOT RLS Maintenance study and a 52-week noncomparative study conducted in Japan. Gabapentin enacarbil was generally well tolerated in adult patients with RLS participating in short- and longer-term clinical trials. The most common treatment-emergent adverse events were somnolence/sedation and dizziness. Most adverse events were of mild to moderate severity, with relatively few patients discontinuing treatment because of an adverse event.

Strategies for the treatment of restless legs syndrome

Restless legs syndrome (RLS) is a common neurological disorder of unknown etiology that is managed by therapy directed at relieving its symptoms. Treatment of patients with milder symptoms that occur intermittently may be treated with nonpharmacological therapy but when not successful, drug therapy should be chosen based on the timing of the symptoms and the needs of the patient. Patients with moderate to severe RLS typically require daily medication to control their symptoms. Although the dopamine agonists, ropinirole and pramipexole have been the drugs of choice for patients with moderate to severe RLS, drug emergent problems like augmentation may limit their use for long term therapy. Keeping the dopamine agonist dose as low as possible, using longer acting dopamine agonists such as the rotigotine patch and maintaining a high serum ferritin level may help prevent the development of augmentation. The α2δ anticonvulsants may now also be considered as drugs of choice for moderate to severe RLS patients. Opioids should be considered for RLS patients, especially for those who have failed other therapies since they are very effective for severe cases. When monitored appropriately, they can be very safe and durable for long term therapy. They should also be strongly considered for treating patients with augmentation as they are very effective for relieving the worsening symptoms that occur when decreasing or eliminating dopamine agonists.

Review of the treatment of restless legs syndrome: focus on gabapentin enacarbil

The FDA approved gabapentin enacarbil in 2011 as the first non-dopaminergic agent for the treatment of restless legs syndrome (RLS) symptoms. Although gabapentin enacarbil is a pro-drug of gabapentin, its pharmacokinetics differ. Absorption of gabapentin enacarbil is more predictable, and inter-patient variability in bioavailability is lower than that of gabapentin. Studies have demonstrated superiority of gabapentin enacarbil compared to placebo. Comparisons to currently available RLS treatments are lacking, but clinical trials demonstrate comparable improvement in RLS symptoms to the dopamine agonists ropinirole and pramipexole, which are usually considered first-line therapy for daily RLS symptoms. Gabapentin enacarbil was well tolerated in clinical trials. The role of the drug in RLS treatment remains undefined, although it will likely be used as an alternative for refractory RLS when other treatments have failed. Additionally, gabapentin enacarbil may be recommended for patients with daily RLS symptoms that are less intense or are associated with pain as an alternative to dopamine agonists.

Dose response of Gabapentin Enacarbil versus placebo in subjects with moderate-to-severe primary restless legs syndrome: an integrated analysis of three 12-week studies

BACKGROUND

The efficacy and tolerability of gabapentin enacarbil (Horizant®; GlaxoSmithKline, Brentford, UK) has been demonstrated in several restless legs syndrome (RLS) phase II and phase III clinical studies at various doses from 600 mg to 2400 mg.

OBJECTIVE

The objective of this study was to evaluate key efficacy and safety outcomes in subjects with RLS treated with once-daily gabapentin enacarbil 600 mg, 1200 mg, 1800 mg and 2400 mg, providing supportive evidence of the efficacy of gabapentin enacarbil 600 mg compared with higher doses and placebo.

STUDY DESIGN

Integrated post hoc analysis of three 12-week, randomized, double-blind, placebo-controlled trials in subjects with RLS.

SETTING

The three studies were carried out at multiple centres in the US.

PATIENTS

In total, 760 subjects were included in the pooled analysis (placebo, n = 245; gabapentin enacarbil 600 mg, n = 163; gabapentin enacarbil 1200 mg, n = 269; gabapentin enacarbil 1800 mg, n = 38; gabapentin enacarbil 2400 mg, n = 45).

INTERVENTION

In all studies, gabapentin enacarbil or placebo was administered once daily at approximately 5 p.m. with food. Gabapentin enacarbil was initiated at a dose of 600 mg with subsequent titration in 600 mg increments every 3 days up to the randomized dose.

MAIN OUTCOME MEASURE

The efficacy endpoints analysed for the purpose of this integrated analysis were change from baseline in International Restless Legs Scale (IRLS) total score and the proportion of responders (subjects rated as 'much' or 'very much' improved) on the investigator-rated Clinical Global Impression-Improvement (CGI-I) scale. Safety endpoints assessed were the incidence of treatment-emergent adverse events (AEs) and serious AEs.

RESULTS

Gabapentin enacarbil 600 mg significantly improved IRLS total score compared with placebo (adjusted mean [standard error] change in IRLS total score from baseline to week 12 last observation carried forward: -13.6 [0.71] vs -9.3 [0.55]; adjusted mean treatment difference: -4.3; 95% CI -6.01, -2.52; p < 0.0001). A significantly higher proportion of subjects was rated as responders on the investigator-rated CGI-I scale with gabapentin enacarbil 600 mg compared with placebo (70.2% vs 42.2%; adjusted odds ratio 3.1; 95% CI 1.96, 4.89; p < 0.0001). Similar treatment benefits were seen with both efficacy endpoints for the three higher doses. The AEs reported most frequently were somnolence and dizziness; there was a dose-response relationship to these AEs. No new or unexpected safety issues were identified by this integrated analysis.

CONCLUSION

The lowest dose of gabapentin enacarbil evaluated (600 mg) significantly improved RLS symptoms compared with placebo. The safety profile was consistent with that described previously in the literature.

The treatment of restless legs syndrome and periodic limb movement disorder in adults--an update for 2012: practice parameters with an evidence-based systematic review and meta-analyses: an American Academy of Sleep Medicine Clinical Practice Guideline

A systematic literature review and meta-analyses (where appropriate) were performed to update the previous AASM practice parameters on the treatments, both dopaminergic and other, of RLS and PLMD. A considerable amount of literature has been published since these previous reviews were performed, necessitating an update of the corresponding practice parameters. Therapies with a STANDARD level of recommendation include pramipexole and ropinirole. Therapies with a GUIDELINE level of recommendation include levodopa with dopa decarboxylase inhibitor, opioids, gabapentin enacarbil, and cabergoline (which has additional caveats for use). Therapies with an OPTION level of recommendation include carbamazepine, gabapentin, pregabalin, clonidine, and for patients with low ferritin levels, iron supplementation. The committee recommends a STANDARD AGAINST the use of pergolide because of the risks of heart valve damage. Therapies for RLS secondary to ESRD, neuropathy, and superficial venous insufficiency are discussed. Lastly, therapies for PLMD are reviewed. However, it should be mentioned that because PLMD therapy typically mimics RLS therapy, the primary focus of this review is therapy for idiopathic RLS.

Role of gabapentin enacarbil XR in restless legs syndrome

Gabapentin enacarbil XR is a new extended-release formulation which attempts to overcome the reduced efficacy of shorter-acting gabapentin, with sustained delivery over a 24-hour period. It is a gabapentin prodrug which is efficiently and rapidly converted to gabapentin during active transport throughout the length of the intestine via high-capacity monocarboxylate type 1 nutrient transporters unlike its predecessor, which is absorbed via low-capacity transporters largely confined to the upper intestinal region. Its lack of saturable absorption allows for dose-proportional absorption and hence increased bioavailability. Several clinical trials addressing its efficacy in moderate to severe restless legs syndrome (RLS) demonstrate improvements in the International RLS Rating Scale after a 2-week to 3-month period. Open-label studies of 52 weeks' duration showed maintenance of symptom reduction with once-daily administration of the extended-release formulation. The most commonly reported treatment-emergent adverse effects were somnolence and dizziness. Although the incidence of emergent adverse effects is high, it is comparable with that of gabapentin. No studies thus far have documented augmentation as an issue, unlike that observed with most dopaminergic agents. In addition, both dopamine precursors and agonists have not been shown to increase slow wave sleep or improve overall sleep architecture consistently despite improvement in the periodic leg movement index, in contrast with gabapentin enacarbil. Presently, gabapentin enacarbil has not been approved by the Therapeutic Goods Administration or Medsafe for use in RLS. The cost of this medication may also be a potential barrier for many patients. Future comparative efficacy studies with gabapentin, first-line dopaminergic agents, rotigotine, being the other once daily RLS medication, and pregabalin, the structural analog of gabapentin, will be necessary.

Long-term efficacy and safety of gabapentin enacarbil in Japanese restless legs syndrome patients

Several short- and long-term studies conducted in Europe/North America have demonstrated good efficacy and tolerability of 600-1800 mg gabapentin enacarbil (GEn). However, no studies have evaluated the efficacy of long-term treatment with GEn in Asian patients. Therefore, the objective of this study was to evaluate the efficacy and safety of long-term treatment with GEn in Japanese patients with restless legs syndrome (RLS) in a multicenter open-label study. RLS patients aged 20-80 years were allocated to receive oral GEn 1200 mg/day for a treatment period of 52 weeks. International Restless Legs Syndrome Scale (IRLS) score, investigator- and patient-rated Clinical Global Impression (CGI) scores, Pittsburgh Sleep Quality Index (PSQI) total scores and subscores, and short form (SF)-36 subscores were assessed, and adverse events (AEs) were monitored. In 181 patients (mean age, 54.9±12.2 years; BMI, 23.0±2.6 kg/m²) IRLS score decreased from 24.4±0.4 at baseline to 6.3±0.6 at week 52, with a reduction of -18.0±0.6. The IRLS responder rate was 80.3% at week 52. ICGI and PCGI responder rates were 87.1% and 87.1%, respectively. PSQI and SF-36 also showed significant improvements. AEs were reported in 96.2% of patients but remained mild-to-moderate in nearly all the cases. Serious AEs occurred in 1.6%. Dizziness and somnolence were noted in 46.2% and 41.2% of patients, respectively, and mostly occurred during the first 4 weeks. No episodes of augmentation were reported. In conclusion, long-term treatment with GEn improved RLS symptoms as well as investigator- and patient-reported outcomes in Japanese patients with moderate-to-severe RLS, with an acceptable safety profile. Randomized, double-blind, placebo/active-controlled trials are desirable to confirm these preliminary results.

Clinical pharmacokinetics of gabapentin after administration of gabapentin enacarbil extended-release tablets in patients with varying degrees of renal function using data from an open-label, single-dose pharmacokinetic study

BACKGROUND

Gabapentin enacarbil, a transported acyloxyalkylcarbamate prodrug of gabapentin, provides predictable and dose-proportional gabapentin exposure (AUC). Gabapentin is cleared via renal excretion, and its elimination is proportional to creatinine clearance (CrCL); CrCL can, therefore, be used as a predictor of gabapentin renal clearance. Gabapentin produced from hydrolysis of gabapentin enacarbil is also eliminated via the renal clearance pathway. It was, therefore, anticipated that the pharmacokinetics of gabapentin derived from gabapentin enacarbil would also be affected by renal function.

OBJECTIVE

The objective of this study was to describe a population pharmacokinetic analysis of gabapentin enacarbil in patients with varying degrees of renal function, using data from an open-label study of gabapentin enacarbil in patients with renal impairment (XenoPort, Inc. protocol XP066), to determine whether dosage adjustments are necessary in patients with renal impairment.

METHODS

Men and women >18 years of age with a body mass index ≤34 kg/m(2) and who were, in general, healthy with the exception of renal impairment were enrolled All patients received a single 600-mg gabapentin enacarbil extended-release tablet under fed conditions. After dosing, plasma, urine, and dialysate samples were analyzed. Safety profile evaluations included adverse events, vital signs, ECGs, and laboratory values. Pharmacokinetic data were compared with those from Phase I-III studies in subjects with normal renal function to evaluate the relationship between gabapentin oral clearance (CL/F) and CrCL.

RESULTS

Fifteen patients (11 men and 4 women) were enrolled. One patient had moderate renal impairment (CrCL 30-59 mL/min), 7 patients had severe renal impairment (CrCL <30 mL/min), and 7 patients had end-stage renal disease (CrCL <15 mL/min). Ten patients were white, 4 were African American, and 1 was American Indian or Alaskan Native. Their mean (range) age was 55 (28-76) years, weight was 85.6 (62-134) kg, and body mass index was 28.3 (22-34) kg/m(2). Mean maximum plasma gabapentin concentration was 5.77 μg/mL in patients with moderate and severe renal impairment, and 5.59 μg/mL in patients with end-stage renal disease who were undergoing hemodialysis. Based on the population pharmacokinetic analysis, gabapentin CL/F after administration of gabapentin enacarbil was proportionally related to CrCL, with an approximately 1.6-fold decrease in CL/F for every 2-fold decrease in CrCL. The most frequent adverse event was dizziness (4 of 15 patients). Other adverse events that were assessed as possibly or probably related to treatment were defecation urgency, extremity pain, feeling of relaxation, and muscle weakness; each occurred in 1 patient only. All events were mild or moderate and resolved without sequelae.

CONCLUSIONS

The data suggest that dosage adjustment for gabapentin enacarbil is necessary in patients with impaired renal function. Gabapentin enacarbil, 600 mg, seemed to be well tolerated in this small selected population.

Anti-epileptic drugs

Therapeutic Reviews aim to provide essential independent information for health professionals about drugs used in palliative and hospice care. Additional content is available on www.palliativedrugs.com. Country-specific books (Hospice and Palliative Care Formulary USA, and Palliative Care Formulary, British and Canadian editions) are also available and can be ordered from www.palliativedrugs.com. The series editors welcome feedback on the articles (hq@palliativedrugs.com).