Inclusion Criteria:  18 to 75 years old. Subjects must have a plan of extraction of impacted tooth. Subjects with moderate to severe pain (VAS score ≥ 50mm).This must be measured within a maximum of 4 hours after the end of extraction of impacted tooth. weight at least 45kg,and no more than 100kg. If a female is of child-bearing potential, she must be using highly effective methods of contraception throughout the study. Willingness to comply with the study procedures and requirements. willing and able to provide written informed consent for this study.  Exclusion Criteria:  any analgesic medication other than preoperative or intraoperative anaesthetic agents within 12h before taking trial medication medication a longacting NSAID within 4 days,or a shortacting NSAID within 1 days prior to dosing. any anti-depressive medication, selective serotonin reuptake inhibitors (SSRIs), diet pills et.al. with 30 days of study entry. Oral surgical site combined with infection. Severe cardiovascular and cerebrovascular diseases. Severe gastrointestinal disease. had a history of seizures or drug or alcohol abuse. uncontrolled hypertension. significant abnormal electrocardiogram significant abnormal laboratory value. Allergic to the study drug and ingredients. Pregnancy, lactation or recent Pregnant plan; Subjects who participated in a clinical research study involving an experimental drug before 30 days of study entry. other conditions unsuitable for participation in the study.