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

Quantitative Comparison of the Efficacies of 5 First-Line Drugs for Primary Restless Leg Syndrome

Comparative analyses of the efficacies of dopaminergic agonists (pramipexole, ropinirole, and rotigotine patch) and α-2-δ ligands (gabapentin enacarbil and pregabalin) for treatment of primary restless leg syndrome (RLS) are lacking because of the few head-to-head clinical trials. A model-based meta-analysis approach was employed to quantitatively compare the efficacies of these 5 first-line RLS drugs. Longitudinal efficacy data of RLS drugs were collected from published eligible literature. Mean changes in both the International Restless Leg Syndrome Study Group (IRLS) rating scale and Clinical Global Impression Improvement (CGI-I) scale response rate were analyzed. A study-level population pharmacodynamic model was used to fit the dose-effect relationship and to describe the therapeutic effect over time for RLS drugs and placebo, and the typical efficacies of these drugs were compared. The onset of action was rapid for RLS drugs. In the placebo group, typical maximum IRLS reduction (E_max,IRLS ) and CGI-I response rate (E_max,CGI-I ) were -9.34 points and 48.2%, respectively. After deducting placebo effects, we found that the baseline IRLS score was significantly correlated with the E_max,IRLS of dopaminergic agonists. Typical E_max,IRLS of dopaminergic agonists was expressed as - 7.7 - 0.682 × ( baseline IRLS score - 24 ) points. Typical E_max,IRLS values of pregabalin and gabapentin enacarbil were -5.95 points and -4.00 points, respectively. The therapeutic effect of dopaminergic agonists was found to be associated with baseline symptom severity. In RLS patients with more severe symptoms, the therapeutic effect of dopaminergic agonists tended to be better than that of α-2-δ ligands.

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.

Nerve Decompression and Restless Legs Syndrome: A Retrospective Analysis

Introduction

Restless legs syndrome (RLS) is a prevalent sleep disorder affecting quality of life and is often comorbid with other neurological diseases, including peripheral neuropathy. The mechanisms related to RLS symptoms remain unclear, and treatment options are often aimed at symptom relief rather than etiology. RLS may present in distinct phenotypes often described as “primary” vs. “secondary” RLS. Secondary RLS is often associated with peripheral neuropathy. Nerve decompression surgery of the common and superficial fibular nerves is used to treat peripheral neuropathy. Anecdotally, surgeons sometimes report improved RLS symptoms following nerve decompression for peripheral neuropathy. The purpose of this retrospective analysis was to quantify the change in symptoms commonly associated with RLS using visual analog scales (VAS).

Methods

Forty-two patients completed VAS scales (0–10) for pain, burning, numbness, tingling, weakness, balance, tightness, aching, pulling, cramping, twitchy/jumpy, uneasy, creepy/crawly, and throbbing, both before and 15 weeks after surgical decompression.

Results

Subjects reported significant improvement among all VAS categories, except for “pulling” (P = 0.14). The change in VAS following surgery was negatively correlated with the pre-surgery VAS for both the summed VAS (r = −0.58, P < 0.001) and the individual VAS scores (all P < 0.01), such that patients who reported the worst symptoms before surgery exhibited relatively greater reductions in symptoms after surgery.

Conclusion

This is the first study to suggest improvement in RLS symptoms following surgical decompression of the common and superficial fibular nerves. Further investigation is needed to quantify improvement using RLS-specific metrics and sleep quality assessments.

Postherpetic neuralgia: epidemiology, pathophysiology, and pain management pharmacology

Herpes zoster, also known as shingles, is a distinctive clinical condition caused by the reactivation of latent varicella zoster (chickenpox) virus following an initial infection. Approximately 1 million cases of herpes zoster occur annually in the US, and one in every three people develops herpes zoster during their lifetime. Postherpetic neuralgia is a neuropathic pain syndrome characterized by pain that persists for months to years after resolution of the herpes zoster rash. It stems from damage to peripheral and central neurons that may be a byproduct of the immune/inflammatory response accompanying varicella zoster virus reactivation. Patients with postherpetic neuralgia report decreased quality of life and interference with activities of daily living. Approaches to management of postherpetic neuralgia include preventing herpes zoster through vaccination and/or antiviral treatment, and administering specific medications to treat pain. Current guidelines recommend treatment of postherpetic neuralgia in a hierarchical manner, with calcium channel α2-δ ligands (gabapentin and pregabalin), tricyclic antidepressants (amitriptyline, nortriptyline, or desipramine), or topical lidocaine patches as first-line drugs. The safety and tolerability of pharmacologic therapies for pain are important issues to consider as postherpetic neuralgia affects primarily an older population. Patients should be educated on appropriate dosing, titration if applicable, the importance of adherence to treatment for optimal effectiveness, and possible side effects. Health-care professionals play a key role in helping to ameliorate the pain caused by postherpetic neuralgia through early recognition and diligent assessment of the problem; recommending evidence-based treatments; and monitoring treatment adherence, adverse events, responses, and expectations. Nurse practitioners are especially crucial in establishing communication with patients and encouraging the initiation of appropriate pain-relieving treatments.

Alpha2delta ligands, gabapentin, pregabalin and mirogabalin: a review of their clinical pharmacology and therapeutic use

INTRODUCTION

The first two alpha₂delta ligands - gabapentin (GBP) and pregabalin (PGB) - were initially synthesized as antiepileptics; however, they were later also found to be useful for the treatment of additional conditions. Areas covered: Relevant publications describing potential underlying mechanisms, clinical pharmacokinetics/pharmacokinetics, and clinical efficacy and safety of these drugs in various disease conditions were searched in PubMed and Scopus and included in this review. Expert commentary: GBP and PGB are effective for the treatment neuropathic pain, fibromyalgia and epilepsy; in addition, they may be useful for the reduction of postoperative pain. PGB is also effective for the treatment of generalized anxiety disorder and GBP for the treatment of restless legs syndrome. GBP may be considered a treatment option for pain associated with Guillain-Barré Syndrome and phantom limb and for the management of uremic pruritus. Mirogabalin (MGB), recently developed, is being investigated for the treatment of peripheral neuropathic pain and fibromyalgia, showing promising results in patients with diabetic peripheral neuropathy. Their most frequent adverse reactions are of neuropsychiatric nature and include fatigue, dizziness, sedation, somnolence, and ataxia; peripheral edema and weight gain are also frequently described. Pharmacokinetic interactions are scarce; however, pharmacodynamic interactions have been described in association with drugs with CNS-depressant effects.

Restless legs syndrome-current therapies and management of augmentation

Idiopathic restless legs syndrome (RLS) can severely affect quality of life and disturb sleep, so that pharmacological treatment is necessary, especially for elderly patients. Treatment guidelines recommend initiation of therapy with dopamine agonists (pramipexole, ropinirole or the rotigotine transdermal patch, all approved in most countries) or α-2-δ ligands (gabapentin enacarbil, approved in the USA and Japan), depending on the country and availability. Where approved, opioids (prolonged release oxycodone-naloxone, approved in Europe) are also recommended as a second-line therapy for severe RLS. Several iron formulations can be effective but are not yet approved for RLS therapy, whereas benzodiazepines and other anticonvulsants are not recommended or approved. Less is known about effective management of RLS that is associated with other conditions, such as uraemia or pregnancy. Furthermore, very little data are available on the management of RLS when first-line treatment fails or patients experience augmentation. In this Review, we summarize state-of-the-art therapies for RLS in the context of the diagnostic criteria and available guidelines, based on knowledge ranging from Class I evidence for the treatment of idiopathic RLS to Class IV evidence for the treatment of complications such as augmentation. We consider therapies, including combination therapies, that are used in clinical practice for long-term management of RLS, despite a lack of trials and approval, and highlight the need for practical long-term evaluation of current trials.

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.

Pharmacological treatment of sleep disorders and its relationship with neuroplasticity

Sleep and wakefulness are regulated by complex brain circuits located in the brain stem, thalamus, subthalamus, hypothalamus, basal forebrain, and cerebral cortex. Wakefulness and NREM and REM sleep are modulated by the interactions between neurotransmitters that promote arousal and neurotransmitters that promote sleep. Various lines of evidence suggest that sleep disorders may negatively affect neuronal plasticity and cognitive function. Pharmacological treatments may alleviate these effects but may also have adverse side effects by themselves. This chapter discusses the relationship between sleep disorders, pharmacological treatments, and brain plasticity, including the treatment of insomnia, hypersomnias such as narcolepsy, restless legs syndrome (RLS), obstructive sleep apnea (OSA), and parasomnias.