Cortical Excitability Changes Induced by Retigabine: a Transcranial Magnetic Stimulation Study

Study Overview
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Brief Summary
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The objective of this study is to characterize the effects of a single-dose of retigabine on cortical excitability in healthy subjects, as quantified by means of TMS.

Detailed Description
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Epilepsy is a disorder of brain excitability. Antiepileptic drugs (AEDs) modulate this excitability and transcranial magnetic stimulation (TMS) imposed itself as one of the best noninvasive methods to study cortical excitability in human subjects. Based on several recent studies, we hypothesize that measuring TMS parameters in the patients suffering from epilepsy can rapidly predict the effectiveness of the newly given AED and, ultimately, guide the optimization of the AED therapy. Characterizing the neurophysiological properties of innovative AEDs such as retigabine with TMS will allow 1) to better understand how AEDs modulate, in vivo, cortical excitability in humans in relation to their mode of action and 2) to establish TMS as a tool for assessing individual responsiveness to a particular AED treatment and for antiepileptic treatment monitoring. The effects of most AEDs on cortical excitability have been investigated. The modifications of the excitability parameters are related to the specific mode of action of each AED. For the new AED retigabine, at least two modes of action are known: 1) increase in cellular potassium efflux by changing conformation of the KV7.2-7.3 channels and 2) enhancement of GABA-A activity.

Official Title
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Cortical Excitability Changes Induced by Retigabine: a Transcranial Magnetic Stimulation Study

Conditions
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Epilepsy

Intervention / Treatment
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* Drug: retigabine
* Drug: placebo


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: age 18-50 years being healthy willing to participate and able to understand study and provide informed consent Exclusion Criteria: intake of psycho-active drugs (AEDS, antidepressants, benzodiazepines, neuroleptics, hypnotics, ...) alcohol or drug abuse antecedent of seizure contra-indication to TMS (metal in the head, skull fracture) contra-indication to retigabine.

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 50 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Basic Science
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: Quadruple


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Active Comparator: Retigabine<br>Administration of a single dose of 400 mg retigabine, two hours before the measures | Drug: retigabine<br>* Single oral administration of a 400 mg tablet.<br>* Other names: ezogabine;|
| Placebo Comparator: placebo<br>Randomized administration of a single dose of placebo, two hours before the measures. | Drug: placebo<br>* Single oral administration of a tablet<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Measurement of TMS cortical excitability parameter before and after drug intake | The primary endpoint is the impact of retigabine on TMS cortical excitability parameters in healthy volunteers compared to placebo, in a double-blind cross-over design. These parameters were specifically chosen according to the known dual mechanism of action of retigabine. Modulation of GABA-A receptors and increase of potassium efflux. The parameters studied are the motor threshold (MT), the amplitude of motor evoked potential (MEP), the cortical silent period (CSP), the short interval intracortical inhibition (SICI), the long interval intracortical inhibition (LICI), the intracortical facilitation (ICF) and the short interval cortical facilitation (SICF). Parameters are registered before and after retigabine or placebo intake. Modifications of these parameters are recorded and compared for retigabine vs placebo for each subject. A group analysis retigabine vs placebo is also performed. | Two hours after oral intake | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Assessing tolerability of a single dose intake of retigabine | Reporting of eventual side effect after the intake of retigabine vs placebo with a structurate questionnaire. | 24 hours after drug intake | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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retigabine, cortical excitability, Transcranial Magnetic Stimulation