A method of stabilising a pharmaceutical composition is described. The pharmaceutical composition comprises a propellant and at least one formoterol compound selected from formoterol, pharmaceutically acceptable salts of formoterol, solvates of formoterol, and solvates of pharmaceutically acceptable salts of formoterol which is dissolved or suspended in the propellant. The method comprises using a propellant comprising at least 90 weight % 1,1-difluoroethane (R-152a).
