the present invention relates to a dual - cannister inhaler for effectively delivering medications by inhalation through the mouth of patients , having a spacer for more effectively mixing the medication and air , and easy to operate lever and canister selection mechanisms . a preferred embodiment of the invention has universal receptors for two metered dose inhaler canisters . a lever arm is provided that is opposed to the body of the inhaler , which allows a patient to use the entire hand to activate the metered dose inhaler canister . a simple and easy to operate sliding selector permits one - handed control of the canister selector . in a preferred embodiment a valve assembly and whistle are included in the inhaler to improve the consistency and effectiveness of delivery of medication to the lungs of a patient .