Pharmacokinetics (PK) of Dalfampridine-ER 7.5 mg BID in Healthy Volunteers and Subjects With Mild or Moderate Renal Impairment

Inclusion Criteria: * Either gender between the ages of 18 and 75 years * Have a body mass index (BMI) ranging between 18.5 - 35.0 kg/m2, inclusive * Have adequate cognitive function to understand and sign the IRB approved informed consent prior to the performance of any study-specific procedures * Be willing and able to comply with all trial requirements * Fit into one of three 12-subject groups: normal renal function (CrCl \> 80 mL/min), mild renal impairment (CrCl 51-80 mL/min), and moderate renal impairment (CrCl 30-50 mL/min) * Have sufficient venous access to permit blood sample collection * Women of childbearing potential must have a negative β-HCG pregnancy test at the Screening Visit. Exclusion Criteria: * Women who are either pregnant or breastfeeding, and women of childbearing potential (i.e., has not had a hysterectomy or bilateral oophorectomy, or is not at least two years postmenopausal) who are engaged in active heterosexual relations and not using any of the following birth control methods: tubal ligation, implantable contraception device, oral, patch or injectible contraceptive, double barrier method, or sexual activity restricted to a vasectomized partner; * History of seizure(s); * Unstable, acute, or severe (CrCl \< 30 mL/min) renal failure; * Clinically significant abnormal findings on the physical examination, ECG, vital signs, medical history, or clinical laboratory results during screening (other than abnormal renal values); * Any unstable cardiovascular, enterohepatic, respiratory, or immunologic disorder or disease that may substantially affect the pharmacokinetics of Dalfampridine-ER; * Known allergy to pyridine-containing substances, or any of the inactive ingredients of the Dalfampridine-ER tablet (colloidal silicon dioxide, hydroxypropyl methylcellulose, magnesium stearate, microcrystalline cellulose, polyethylene glycol, and titanium dioxide); * Participation in an investigational drug trial 30 days prior to Screening or plans to enroll in an investigational drug trial at any time during this study; * Any medical condition including psychiatric disease that would interfere with the interpretation of the study results or the conduct of the study; * Subject has started a new medication (prescription, vitamins, herbal medications, or other over-the-counter medications), or had a change in their existing medication within 30 days prior to screening; * History of drug or alcohol abuse in the past 2 years, or tests positive for drugs of abuse at Screening; * Donation of blood or blood components within 30 days prior to administration of investigational drug. The Investigator should instruct subjects who participate in this study not to donate blood or blood components during their participation in the study and up to four weeks after the completion of the study.