Efficacy and Safety Study of Procaterol Hydrochloride to Treat Patients With Cough Variant Asthma (CVA)

Inclusion Criteria: * male or female patients,18-75 years old; * cough lasting over 3 weeks ; dry cough or with slight white mucous phlegm; cough is the main clinical symptom or the only symptom; * without wheeze and fever; * without the history of upper respiratory tract infection within recent two months; non-smoking or giving-up smoking for over two years; * without rales from lung; * no obvious abnormalities from chest X-ray; * bronchial provocation test: positive. Exclusion Criteria: * patients with chronic pulmonary disease; * patients who are allergic to ß2 receptor agonist; * patients taking ß2 receptor agonist for long time; * severe heart, renal and hepatic disease; * unable to comply with the protocol; * pregnant, breast feeding, and childbearing potential women; * patients improper to the trial according to the investigators' judgment.