Gabapentin enacarbil - clinical efficacy in restless legs syndrome

The Critical Role of Passive Permeability in Designing Successful Drugs

Passive permeability is a key property in drug disposition and delivery. It is critical for gastrointestinal absorption, brain penetration, renal reabsorption, defining clearance mechanisms and drug-drug interactions. Passive diffusion rate is translatable across tissues and animal species, while the extent of absorption is dependent on drug properties, as well as in vivo physiology/pathophysiology. Design principles have been developed to guide medicinal chemistry to enhance absorption, which combine the balance of aqueous solubility, permeability and the sometimes unfavorable compound characteristic demanded by the target. Permeability assays have been implemented that enable rapid development of structure-permeability relationships for absorption improvement. Future advances in assay development to reduce nonspecific binding and improve mass balance will enable more accurately measurement of passive permeability. Design principles that integrate potency, selectivity, passive permeability and other ADMET properties facilitate rapid advancement of successful drug candidates to patients.

Encapsulation of secondary and tertiary ammonium salts by resorcinarenes and pyrogallarenes: the effect of size and charge concentration

Multiple weak interactions are manifested in the complexation of different categories of secondary and tertiary alkyl ammonium salts with resorcinarenes and pyrogallarene leading to open inclusion and dimeric capsular assemblies with varying binding affinities, and analyzed in solid, liquid and gas phases.

ADMET considerations for restless leg syndrome drug treatments

INTRODUCTION

Restless legs syndrome (RLS) is a common neurological disorder that might impair nocturnal rest causing decreased alertness, depressed mood, reduced job performance, and poor quality of life. In patients affected by severe RLS, a pharmacological treatment is mandatory.

AREAS COVERED

The present review is based on a search using PubMed from 1994 to 2012. It is focused on the Absorption, Distribution, Metabolism, Elimination and Toxicology (ADMET) characteristics of the most used medications for RLS. In particular, the ADMET characteristics of dopaminergic agents, anticonvulsants able to improve neuropathic pain, and iron were discussed.

EXPERT OPINION

Clinical trials have showed that non-ergolic dopamine agonists are efficacious and safe for patients affected by moderate to severe idiopathic RLS. However, no head-to-head study has compared the long-term effects of the three dopamine agonists approved by the FDA for RLS (ropinirole, pramipexole, and rotigotine). Moreover, further studies should investigate the extended-release formulation of ropinirole and pramipexole in RLS patients affected by all day long distressing symptoms. A standardized treatment for symptomatic forms of RLS is lacking. Randomized, placebo-controlled trials should be performed at least in RLS patients with peripheral neuropathic and chronic kidney disease. Concerning RLS due to iron deficiency, a head-to-head study comparing efficacy, safety and compliance of oral iron versus intravenous one seems to be needed.

The effect of selenium administration on restless leg syndrome treatment

BACKGROUND

Restless leg syndrome (RLS) is defined as an uncomfortable feeling in the limbs which is prominently sensed in legs. Dopamine system involvement is considered as the base of RLS's etiology. Because of safety, anti-oxidant and dopaminergic promoting action of selenium, this study aims to investigate the effect of selenium on restless leg syndrome treatment.

METHODS

Sixty patients with primary RLS were enrolled in this clinical trial (Irct2011103015943n1). It was based on 3 periods of drug prescription with one month wash out period. As placebo, 50 and 200 μg of selenium were administered in each separated month. The diagnosis was based on criteria published by IRLSG (International RLS Study Group). The questionnaire included 10 questions while each question's rating was between 0 and 4. Points between 1 and 10 were considered mild, 11 to 20 as moderate, 21 to 30 as severe and 31 to 40 as very severe. After end of each month of drug consumption, questionnaires were completed and each subject was asked to report the severity of disease and side effects of the drugs. At least 10 declines in scale were considered as appropriate responses.

RESULTS

Improvement (decline IRLS score >10) was significantly higher in selenium (50 and 200 μg) than placebo group.

CONCLUSION

Selenium prescription in daily recommended dose of 50 μg instead of a dopamine agonist would be an alternative treatment in improvement of RLS symptoms.

New Drug Review: Gabapentin enacarbil extended release (Horizant™) – A new formulation on the horizon

Gabapentin enacarbil was approved by the Food and Drug Administration (FDA) in April of 2011. This article reviews clinically significant aspects of this new drug including: the FDA-approved indications, mechanism of action, administration, drug interactions, adverse effects, clinical trial evidence, innovative properties and place in therapy.

Gabapentin Enacarbil: Pharmacotherapy of Restless Legs Syndrome

Restless Legs Syndrome (RLS) is a prevalent sleep-associated movement disorder greatly affecting patients’ quality of life (QoL). Several drugs can be used to control this condition although the first-line dopamine agents often cause adverse effects. Non-dopaminergic drugs such as oral gabapentin (GBP) have been more recently advocated. Despite ameliorating RLS symptoms, GBP’s pharmacokinetic limitations restrict its overall effectiveness. A novel specifically designed prodrug, gabapentin enacarbil (GE), has demonstrated successful RLS alleviation with a superior pharmacokinetic profile. This review aims to examine the efficacy and tolerability of both GBP and GE as pharmacotherapy for RLS. Despite some heterogeneity and limitations across research methodologies, GE appears to be a potential RLS therapy superior to GBP and other dopaminergic agents.