YM872 is an acetic acid monohydrate. It is a potent and selective AMPA receptor antagonist for the treatment of ischemic stroke. YM872 has shown significant neuroprotective effects in animal stroke models ranges that are generally well tolerated on the basis of the results of several toxicology studies. During the treatment period for each dose level, patients will be hospitalized for the 6 hour or 24 hour continuous infusion of study g=drug and for safety monitoring for an additional 24 hours. During the 30-hour treatment period for Part 3 and 48-hour treatment period for Part 4 of the study, safety and efficacy-related assessments will be performed, as well as periodic venipuncture for collection of blood for YM872 plasma concentration determinations. A patient can be discharged at any time after completion of the treatment period of the patient's medical and neurological status permits and once a pre-discharge evaluation has been complete. The safety of YM872 will be evaluated by monitoring for adverse experiences, frequent neurological checks, level of sedation, pulse oximetry, 12-lead EKGs, and clinical laboratory test results. Cardiac telemetry will also be performed. The adverse event profile in healthy study patients has been limited to CNS, with mild CNS effects preceding the appearance of moderate to severe CNS effects. YM872 must be protected from light. YM872 should not be given with general anesthetic, anti-convulsants, benzodiazepines, and sedative/hypnotics. If any of the prohibited drugs are required to treat an emergent condition during study, drug administration should be immediately discontinued, pulmonary function closely monitored and artificial ventilation instituted if needed.