A pharmaceutical composition suitable for use with a metered dose inhaler (MDI) comprises (1). A drug component comprising at least one tiotropium compound selected from tiotropium and the pharmaceutically acceptable derivatives thereof； and (ii) a propellant component comprising 1,1- difluoroethane (HFA-152a). Preferably, the tiotropium compound is tiotropium bromide or tiotropium bromide monohydrate. Preferably, the composition also contains a long acting beta-2-agonist (LABA) (e.g. formoterol, salmeterol, olodaterol). Preferably, the composition also contains a corticosteroid (e.g. budesonide, mometasone, beclomethasone, fluticasone). Preferably, the composition comprises a surfactant (e.g. PVP, polyethylene glycol (PEG), oleic acid, lecithin). The composition may contain a polar excipient such as ethanol. Most preferably, the composition contains less than 5 ppm water. It is claimed that the use of HFA-152a increases the stability, and aerosolisation performance after storage, of the composition relative to the use of other HFA compounds.
