Tiotropium bromide is an organic bromide salt having (1alpha,2beta,4beta,5alpha,7beta)-7-[(hydroxydi-2-thienylacetyl)oxy]-9,9-dimethyl-3-oxa-9-azoniatricyclo[3.3.1.0(2,4)]nonane as the counterion. Used (in the form of the hydrate) for maintenance treatment of airflow obstruction in patients with chronic obstructive pulmonary disease. It has a role as a bronchodilator agent and a muscarinic antagonist. It is an organic bromide salt and a quaternary ammonium salt.