Used in diagnostic testing for asthma and airway hyperresponsiveness. Administered during bronchial challenge tests to assess how sensitive the airways are to stimuli. When inhaled, it causes bronchoconstriction in individuals with reactive airways, helping clinicians confirm asthma when symptoms and baseline lung function tests are inconclusive. The degree of airflow reduction is measured using spirometry, allowing for evaluation of airway responsiveness. Due to its potent effect on smooth muscle contraction, it is used under controlled medical settings where bronchospasm can be safely monitored and reversed if needed.