Inclusion Criteria:

• Males/females at least 18 years old and < 65 years old, capable of understanding and complying with the protocol, including speaking and writing fluent English and having at least a 9th grade education
• Clinically definite diagnosis per McDonald criteria of Multiple Sclerosis as confirmed by the Investigator (Relapsing-Remitting or Secondary Progressive)
• Stable disease and relapse-free for > 90 days as verified by Investigator
• Presence of cognitive deficit as measured score of -1.5 SD on the SDMT (oral version) or a score of -1.0 SD on the SDMT and -1.0 SD on either CVLT-II (total learning or delayed recall) or PASAT
• EDSS <= 6.5
• Standard score of >79 on the WRAT-4 Reading test
• Have given written informed consent prior to any study-related procedure not part of normal medical care, with the understanding that consent may be withdrawn by the subject at any time without prejudice to his/her future medical care
• Capable of performing the requirements of a neuropsychological test battery including having at least 20/70 near visual acuity by near vision chart, with correction (i.e., eyeglasses) allowed
• If female, must neither be pregnant nor breast-feeding and she must either (a) be > 12 months post-menopausal or surgically sterilized or (b) must agree to use an acceptable method of birth control (including hormonal contraceptives, intra-uterine device, or barrier methods such as condoms, diaphragm, etc. with spermicide) for the duration of the study. Abstinence will not be considered an acceptable method of birth control.

Exclusion Criteria:

• Subjects with memory deficits caused by concomitant medication usage or other significant neurological/psychological disease, e.g., Alzheimer's disease, Parkinson's disease, stroke, TIA, Multi-infarct dementia, Huntington's disease, head trauma, or chronic CNS infection
• Evidence of other medical cause of dementia
• Evidence of Major Depressive Disorder as determined by a Beck Fast Screen core of >3 and clinician interview
• Use of the following medications: Antipsychotic agents, Centrally acting appetite suppression drugs (e.g., sibutramine), CNS stimulants or drugs that metabolize to them (e.g., amantadine, Concerta, methylphenidate, Adderall, ephedrine, selegiline), Strattera (atomoxetine), Tricyclic antidepressants (e.g., amitriptyline), Herbal preparations including Ginkgo Biloba or containing Ephedra or other stimulants, MAO inhibitors. Note: other medications may be excluded or permitted, depending on length of treatment and stability of dose
• Uncontrolled or labile hypertension, or any clinically significant, unstable, or major concomitant disorder as determined by the Principal Investigator
• Active malignancy within one year of study participation
• Known human immunodeficiency virus (HIV)
• Current diagnosis of unstable glaucoma
• History of myocardial infarction of symptomatic Coronary Artery Disease
• Evidence of ongoing ischemia or uncontrolled atrial or ventricular arrhythmias as shown by ECG
• History of epilepsy or other seizure disorders
• Clinically significant motor or speech residual neurological deficits (e.g., hemiparesis, aphasia) that interfere with completion of study procedures
• Baseline clinical laboratory values indicative of a clinically significant co-morbidity
• Significant recent history of (within past 12 months) or current drug or alcohol abuse (as defined by DSM-IV)
• Known allergy or hypersensitivity to amphetamines or other sympathomimetic amines
• Participation in any clinical trial with an investigational drug within 30 days prior to randomization
• In the opinion of the Principal Investigator should not participate in the study