Inclusion Criteria:

• Written informed consent is obtained
• Males and/or females; females of childbearing potential, who are not currently pregnant, must agree to use a medically accepted method of contraception throughout the study (i.e., oral contraception, intra- uterine device, or a long-acting injectable form of contraception). Barrier methods alone (i.e., condom) are not adequate.
• Age > 18 years to ≤ 80 years
• Patients with moderate to severe primary RLS
• Stable dose of Pramipexole, between 0.25 mg and 0.75mg, for Restless Legs Syndrome for 4 weeks prior to enrollment
• IRLS >15 (before pramipexole was initiated)

Exclusion Criteria:

Anyone who does not fit the criteria stated under "Inclusion Criteria" and anyone who is included in the following criteria:

• Currently taking neuroleptic medications
• Currently taking dopamine blocking anti-emetic medications.
• Currently taking any drug known to substantially inhibit CYP1A2 (e.g., cimetidine, fluvoxamine) or induce CYP1A2 (e.g., omeprazole) (Note: Subjects already on these agents may be enrolled, but must remain on stable doses of the agents from (Visit 1) 14 days prior to Baseline to the end of the study.
• Current hallucinations
• History of disabling hallucinations or hallucinations in past requiring treatment
• Mini-Mental status examination score < 25 on a scale of 30
• Orthostatic hypotension >30 systolic drop and >20 diastolic drop
• On cholinesterase inhibitors or memantine
• Troublesome edema due to any reason
• Epworth sleepiness scale >8
• Another primary sleep disorder (e.g. obstructive sleep apnea, narcolepsy)
• Secondary causes of RLS (iron deficiency, renal failure)
• Unstable medical conditions as determined by the investigator
• Inadequately managed depression (patient on antidepressants must be on stable dose for 4 weeks prior to enrollment)
• Other stable medical conditions which may interfere with patient evaluation
• Female who is pregnant or lactating
• Use of an investigational drug within the last 30 days