Inclusion Criteria:

• Patients who have suffered an acute ischemic stroke and can be evaluated and treatment initiated within 6 hours after the onset of symptoms (Onset is defined as the time that which the patient was last seen in a normal state, or bedtime for unwitnessed strokes occurring during the night).
• Patients who have a three dimensionally measurable lesion compatible with an acute ischemic stroke measured using MRI.
• Patients who have a National Institutes of Health Stroke Scale (NIHSS) score of at least 7 but not more than 23 and who are conscious.
• Patients who are able to provide written informed consent or have consent provided by a legally authorized representative.
• Patients who are at least 18 years of age.
• Other criteria as specified in the study protocol

Exclusion Criteria:

• Patients who have received alteplase (t-PA) for the current stroke episode. It is assumed that all patients who are eligible will receive treatment with t-PA.
• Patients who have disability and functional limitations prior to the current stroke episode (e.g. deficit resulting from a prior stroke).
• Patients who have brain hemorrhage.
• Patients who have stroke of the brainstem or cerebellum.
• Patients who cannot be evaluated using MRI due to the presence of a pacemaker, claustrophobia, need for sedation, etc.
• Patients who have renal (kidney) disease or insufficiency.
• Patients who have active epilepsy or convulsions during the current stroke episode.
• Patients who are IV drug users or are inebriated.
• Patients who have a history of drug-related anaphylaxis.
• Patients who have taken sedatives, anticonvulsants, or any medication with sedating effects in the 10 days prior study enrollment.
• Patients who have taken more than 1.3 g of aspirin per day in the 2 days prior to enrollment.
• Patients who have a known vitamin hypersensitivity.
• Other exclusion criteria as specified by the study protocol.