A Clinical Trial to Compare the Efficacy and Safety of 1-week Treatment of Intravenous N-acetylcysteine (NAC) 600 mg Twice Daily, Ambroxol Hydrochloride 30 mg Twice Daily and Placebo as Expectorant Therapies in Adult Chinese Patients With Respiratory Tract Diseases and Abnormal Mucus Secretions

Wuxi Peoples' Hospital affiliated to Nanjing Medical University, Wuxi

Inner Mongolia Baogang Hospital, Baotou

Beijing Hospital, Beijing

Beijing Tongren Hospital, Beijing

China-Japan Friendship Hospital, Beijing

Peking University Shougang Hospital, Beijing

Jilin Province People's Hospital, Changchun

The First Bethune Hospital of Jilin University, Changchun

Chengdu Fifth People's Hospital, Chengdu

West China Hospital, Sichuan University, Chengdu

The First Affiliated Hospital of Chongqing Medical University, Chongqing

Deyang People's Hospital, Deyang

Inner Mongolia People's Hospital, Hohhot

Jinhua city central hospital/Jinhua hospital ,School of Medicine,Zhejiang UNIVERSITY, Jinhua

Nanchang University-The Second Affiliated Hospital, Nanchang

Nanjing First Hospital, Nanjing

Zhongda Hospital, Southeast University - Pulmonology, Nanjing

Jiangxi Pingxiang People's Hospital, Pingxiang

Qingdao Municipal Hospital, Qingdao

Minhang District Central Hospital, Shanghai

Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai

Shanghai General Hospital, Shanghai

Shanghai Pulmonary Hospital, Shanghai

Suining Central Hospital, Suining

First Hospital of Shanxi Medical University, Taiyuan

The First Hospital of Shanxi Medical University, Taiyuan

Tongji Hospital, Tongji Medical College of Huazhong University Science and Technology, Wuhan

Wuxi Peoples' Hospital affiliated to Nanjing Medical University, Wuxi

Yangzhou First People's Hospital, Yangzhou

General Hospital of Ningxia Medical University, Yinchuan

Affiliated Hospital of Guangdong Medical University - Respiration, Zhanjiang

The First People's Hospital of Zigong, Zigong