Table 2 Patients’ inclusion and exclusion criteria

Inclusion criteria

 1. Diagnosis of acute bronchitis

 2. Phlegm-heat obstructing lungs syndrome in traditional Chinese medicine Zheng

 3. Total cough symptom score ≥ 4 points

 4. Expectoration in traditional Chinese medicine symptom score ≥ 6 points

 5. Bronchitis severity score ≥ 6 points

 6. Disease course within 72 h

 7. Aged 18 to 65 years old

 8. Voluntarily provide written and informed consent

Exclusion criteria

 1. Patients with respiratory diseases such as chronic obstructive pulmonary disease, bronchiectasis, asthma, lung cancer, tuberculosis, pneumonia, lung abscess, and chest X-ray showing lung inflammation lesions

 2. Patients with severe underlying cardiac, cerebral, hematological, hepatic, or renal disorders or other diseases significantly affecting the survival and prognosis, such as cancer

 3. Current smokers or recent ex-smokers quitting smoking less than 1 month ago

 4. Use of an angiotensin-converting enzyme inhibitor in the last 1 month

 5. Patients with body temperature ≥ 38.5 °C

 6. ALT or AST > 1.5 times of normal upper limit, urine protein >+, serum creatine abnormality, white blood cell count < 3 × 10⁹/L or > 10 × 10⁹/L, and/or neutrophil granulocyte > 80%, or those who need antibiotic therapy

 7. Those who have used other medicines after disease onset including antibiotics, expectorants, antitussives, systemic or inhaled corticosteroids, inhaled bronchodilators, Chinese medicines of relieving exterior syndrome with pungent-cool drugs, clearing away heat, and detoxification and other related Chinese medicines

 8. Pregnant or lactating women and those who have pregnancy plans in the last 3 months

 9. Allergic constitution or known to be allergic to any ingredients in tested drug

 10. Mental patients or legal disability

 11. Patients who have participated or are currently participating in another clinical trial in the last 1 month

 12. Patients who are inappropriate for participation judged by researchers