The purpose of this study is evaluate the efficay and safety of benzonatate soft capsules for improving adult cough symtoms.

The purpose of this study is evaluate the efficay and safety of benzonatate soft capsules for improving adult cough symtoms. The study was designed to be randomized, double-blind, placebo-controlled.Subjects were randomly assigned to the benzonatate soft capsule group and the placebo group on a 1:1 basis。According to the regulatory requirements, 200 cases were planned to be included. Considering that poor efficacy of the placebo control group might lead to shedding, a 10% increase in shedding was achieved, and 220 cases were finally determined, with 110 cases in each group.

Inclusion Criteria:

1. age between 18 and 75 years of age;
2. the onset time is more than 3 days and less than 8 weeks;
3. dry cough, the total score of cough symptom in day and night is greater than 4;
4. Willing to sign informed consent.

Exclusion Criteria:

1. allergic person or known to the test drug containing ingredients (including benzo, soybean oil, glycerin, gelatin) allergy;
2. the cough symptoms are caused by bronchial asthma, tuberculosis, pneumoconiosis, bronchiectasis, tumor and other diseases that have been clearly diagnosed.
3. coughers caused by drugs;
4. respiratory depression or airway obstruction;
5. patients with uncontrolled diabetes or hypertension;
6. having difficulty in swallowing or affecting drug absorption, such as active peptic ulcer and acute gastritis;
7. patients with severe hematopoietic system, nervous system, mental illness (including alcohol and substance abuse) or immunodeficiency diseases;
8. laboratory examination results are abnormal with clinical significance, among which: A.C r is higher than normal value; B.A LT and/or AST>2 times normal value upper limit (ULN).
9. women during pregnancy or lactation or women who are preparing for pregnancy or lactation during the trial;
10. in the first 3 months of screening, any other experimental drug treatment was accepted;
11. Failure to comply with test plans or other conditions that other researchers believe is not appropriate for the group.