A pharmaceutical composition suitable for use with a metered dose inhaler (MDI) comprises: (i) at least one formoterol compound selected from formoterol, pharmaceutically acceptable salts of formoterol, prodrugs of formoterol, solvates of formoterol, solvates of pharmaceutically acceptable salts of formoterol and solvates of prodrugs of formoterol； (ii) at least one corticosteroid； (iii) a surfactant component comprising at least one surfactant compound； and (iv) a propellant component comprising 1,1-difluoroethane (R-152a). The composition may comprise a polar excipient (e.g. ethanol). Preferably, the formoterol compound is formoterol fumarate dihydrate. Preferably the corticosteroid is one of； budesonide, mometasone, beclomethasone, fluticasone. Most preferably, the corticosteroid is budesonide. The surfactant compound is preferably one of； polyvinylpyrrolidone (PVP), polyethylene glycol (PEG), oleic acid, lecithin. Also claimed is a method of stabilising a pharmaceutical composition comprising formoterol through use of R-152a as propellant component.
