Blinded, Randomized Study of Gabapentin (Neurontin®) and Gabapentin Enacarbil (Horizant™) in Restless Leg Syndrome

The study will compare the safety, effectiveness and tolerability of gabapentin (Neurontin)
versus gabapentin enacarbil (Horizant) as treatment restless leg syndrome. Subjects will be
randomized to gabapentin (IR) or Horizant™ (ER). Dosing will be blinded to both patient and
study team members. Once study medication dosing has been optimized, subjects will then
remain on a stable dose for six weeks until study endpoint, after which subjects will be
down-titrated off of study medications.

Inclusion Criteria:

1. Outpatients with a diagnosis of primary restless leg syndrome using the International
Restless Legs Syndrome Study Group (IRLSSG) diagnostic criteria8.

2. RLS symptoms ≥ 15 nights of the month prior to study enrollment and for ≥ 4 of 7
consecutive nights in the week prior to study enrollment (if untreated).

3. Age 18 years to 80 years.

4. International Restless Legs Scale (IRLS) Total severity score of ≥ 15 (moderate to
severe severity). 8

5. Had significant sleep disturbance on item 4 of IRLS.8

6. Women of child-bearing potential must use a reliable method of contraception.

7. Informed consent. Subject must be willing and able to complete all study procedures.

Exclusion Criteria:

1. Any illness that in the investigator's opinion preclude participation in this study.

2. Subjects with non-RLS-related sleep disorders (e.g., sleep apnea)

3. Subjects with neurological diseases or movement disorders other than RLS (e.g.,
diabetic neuropathy, Parkinson's disease, multiple sclerosis, dyskinesias, and
dystonias)

4. Pregnancy or lactation.

5. Concurrent participation in another clinical study.

6. Dementia or other psychiatric illness that prevents the patient from giving informed
consent (Mini-Mental State Examination scores less than 27).

7. Legal incapacity or limited legal capacity.

8. History of RLS symptom augmentation or early-morning rebound with previous
dopamine-agonist treatment.

9. Clinically significant abnormalities in renal function. 3,8,10

10. Presence of severe cardiovascular or pulmonary disease, bronchial asthma, renal,
hepatic or endocrine disease.

11. Concomitant treatment with drugs known to affect sleep/wake, RLS or periodic limb
movements, including antidepressants. Subjects receiving treatment for RLS at
screening will be required to discontinue and wash out for a minimum of 5 half-lives.

12. Body mass index greater than 34 kg/m2.