A flexible bag aerosol holding chamber is sealed around the outlet passage of the actuator for a pressurized metered-dose inhaler. An elastic-loaded mouthpiece is sealed around the inlet passage of the actuator so that the user may intermittently break the seal around the inlet passage by withdrawing the mouthpiece, thus allowing inhalation of a portion of the aerosol contents of the chamber. In a preferred embodiment of the invention, the aerosol contains a compound which has traditionally been smoked such as nicotine or a cannabinoid. The user may draw upon the chamber's contents a number of times at a frequency analogous to smoking until the chamber is fully collapsed. One inhaler actuation, and one filled chamber, are comparable to one cigarette. The collapsible bag chamber allows for economy of inhaler actuations relative to user inhalations, without the aerosol being diluted by ambient air.