A Multicenter, Double-Blind, Placebo Controlled, Phase Ⅱa clinical trial to enroll 120 patients with Vertigo Caused By Posterior Circulation Infarction during 7 days, then to evaluate the efficacy of different dose of Levophencynonate Hydrochloric, and provide the effective dosage for phase IIb clinical study, to study the safety of Levophencynonate Hydrochloric.

This study will conduct in 15 sites to enrolled 120 patients with vertigo under 7 days treatment and 7 days follow-up. The study includes three arms: high dose, low dose and placebo control.To observe the efficacy by change of vertigo severity and duration,and safety by vital sign,adverse event,etc.

Inclusion Criteria:

1. At the age more than 18 years old male or female;
2. Patients with vertigo caused by Posterior Circulation Infarction.
3. Patients diagnosed Posterior Circulation Infarction based on the criteria of Posterior Circulation Ischemia of America;
4. Meet the diagnose criteria of vertigo: Visual Motion (External Vertigo), or Rotation, Swing, Lift and Tilt Sensation (Internal Vertigo);
5. Ability to sign the statements of informed consent;

Exclusion Criteria:

1. Female patients having Pregnant, Lactating or Birth plan recently;
2. Non-posterior circulation infarction patients;
3. Vertigo caused by any other diseases;
4. Long-term alcohol abuse, or drug abuse;
5. Been in critical condition, difficult to make a precise evaluation of efficacy and safety of new drugs;
6. History of allergies on Levophencynonate Hydrochloric or these compositions;
7. Participation in another clinical trial in three months;
8. Investigator thought that should be excluded due to other reason;