The present invention provides a compound which is a hydroxyquinolinone derivative of formula (I),in the form of a racemate, a stereoisomer or a mixture of stereoisomers, or a pharmaceutically acceptable salt or solvate thereof, for use in a method of treating a pulmonary disease or condition associated with β2 adrenergic receptor activity in a mammal, in which the compound is administered by the inhalatory route at a metered nominal dose of less than 5 μg.
