A 63-year-old m an suddenly collapsed at home and was brought unconscious to the emergency department. Physical examination showed a comatose patient with flaccid paralysis on both left extremities. Vital signs were blood pressure 132/70 m m Hg, pulse 90 bpm , respirations 8 breaths/ m in. A diffusion magnetic resonance imaging (MRI) scan disclosed complete occlusion of the right internal carotid artery. Emergency therapy was ordered. Which of the following drugs was most likely included in the emergency treatment of this patient?