A pharmaceutical composition is described. The composition comprises: (i) a drug component comprising at least one salmeterol compound (preferably, salmeterol xinafoate) selected from salmeterol and the pharmaceutically acceptable derivatives thereof； and (ii) a propellant component comprising 1,1-difluoroethane (HFA-152a). Preferably, the composition comprises a long acting muscarinic antagonist (LAMA) such as umeciidinium, ipratropium, tiotropium, aclidinium or glycopyrrolate. Preferably, the composition contains at least one corticosteroid (budesonide, mometasone, beclomethasone, fluticasone). Preferably, the composition comprises a surfactant (polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), oleic acid, lecithin). Composition may further comprise ethanol or other polar excipient. Most preferably, the composition contains less than 5 ppm water. It is claimed that the use of HFA-152a improves the stability of the drug compound relative to the use of other HFA propellants (e.g. HFA-134a). The composition may be used to treat asthma and COPD.
