The Effect of Horizant (Gabapentin Enacarbil) on Augmentation

To Examine the Effect of Horizant (Gabapentin Enacarbil) in Primary Restless Legs Syndrome (RLS) Patients Who Are on Dopaminergic Agents and Exhibiting Augmentation

Restless Legs Syndrome (RLS) is a common neurological disorder. Augmentation is the main complication during long-term DA treatment of RLS. This study aims to examine effect of Horizant (Gabapentin Enacarbil) on Augmentation in RLS patients.

This is an Open label single arm study. The purpose of the study is to demonstrate the efficacy of Horizant in patients with RLS who exhibit augmentation while on Dopaminergic therapy. Adult patients (age 18-85 years) with diagnosis of primary RLS (diagnosed by study investigators) with augmentation on dopaminergic therapy will be screened for participation in the study. RLS diagnosis will be made by the study investigators using International RLS study group criteria. Patients with augmentation on dopaminergic therapy as defined by NIH 2007 with ASRS of 5 to 15 will be offered to participate in the study. Inclusion and exclusion criteria are listed below. The study will be performed after approval of the Institutional Review Board of the University of Missouri.

A total of 50 subjects will be entered into the study over a period of 1 year. Written consent will be obtained from all patients. After pre-participation evaluation for eligibility, subjects will be selected and enrolled in the study and followed for a total of 6 follow up visits (Days 0, 30, 90, 120, 180, 360). Subjects Enrollment period will last up to 12 months. The total duration of study will be 24 months.

Inclusion Criteria:

1. Adult patients with diagnosis of RLS for more than one year.
2. Patients who are on DA therapy for 6 months or longer.
3. Patients who developed Augmentation (on stable dose of DA) lasting for 3 months or longer.
4. Augmentation severity rating scale of 5 to 15.
5. Both males and females
6. Age range = 18-85 year

Exclusion Criteria:

• Known Hypersensitivity to Horizant or Gabapentin products
• Peripheral neuropathy
• Radiculopathy
• Peripheral vascular disease
• Uremia [abnormal blood urea nitrogen (BUN) or Creatinine on Comprehensive Metabolic Panel (CMP)]
• Anemia
• Patients who are currently pregnant
• Patients who currently take opioids, lithium, anti-nausea medications (e.g. metoclopramide), dopaminergic antagonists (e.g. Haloperidol), 1st generation antihistamines (e.g. diphenhydramine, pseudoephedrine), anti-psychotic medications and iron therapy.
• Subjects with impaired decision making capability.