Inclusion Criteria1. Patients with angiographically documented vertebrobasilar artery occlusion
2. Initiation of study drug treatment within 24 hours of the onset of neurological symptoms
3. Age 18-75 (inclusive).
Exclusion Criteria1. Patients with coma > 6 hrs duration and complete loss of brain stem reflexes (corneal reflex, gag reflex, VOR, pupil reflexes) as measured at the last assessment before sedation/intubation
2. Rapidly improving neurologic signs at any time before initiation of study drug administration.
3. Known contrast agent-sensitivity
4. Uncontrolled hypertension defined as a systolic blood pressure > 180 mm Hg or a diastolic blood pressure > 100 mm Hg on 3 separate occasions at least 10 minutes apart or requiring continuous IV therapy.
5. History of stroke within the previous 6 weeks.