Aerosol formulations comprising glycopyrronium chloride in combination with formoterol may be administered by means of a pressurized metered dose inhaler (pMDI) for the prevention or treatment of chronic obstructive pulmonary disease. The formulation further comprises a HFA propellant, a co-solvent, and an amount of inorganic acid sufficient to stabilize both the glycopyrronium chloride and the formoterol components. Optionally, the formulation may further comprise beclometasone dipropionate.
