A mouthpiece configured to be removably coupled with a nebulizer to deliver nebulized medicament to the airway of a subject, the mouthpiece comprising: a nebulizer interface configured to releasably engage an outlet of a nebulizer through which the nebulizer outputs nebulized medicament; a subject interface suitable for engagement by the mouth of the subject and for communicating the interior of the mouthpiece with the airway of the subject; a medicament flow path configured to place the nebulizer interface in fluid communication with the subject interface to facilitate a flow of nebulized medicament from the nebulizer interface to the subject interface and into the airway of the subject through the subject interface; an exhaust outlet; an exhaust flow path configured to place the subject interface in fluid communication with the exhaust outlet to facilitate a flow of exhaled gas from the subject interface to the exhaust outlet and out of the mouthpiece through the exhaust outlet; an inlet valve configured to communicate ambient air with the medicament flow path, wherein the inlet valve is a one-way valve that permits flow fromambient atmosphere into the medicament flow path; and an exhaust valve that controls gas flow within the exhaust flow path, wherein the outlet valve is a one-way valve that permits flow out of the exhaust outlet, characterized in that the mouthpiece further comprises a dividing structure that physically separates the medicament flow path from the exhaust flow path. a nebulizer interface configured to releasably engage an outlet of a nebulizer through which the nebulizer outputs nebulized medicament; a subject interface suitable for engagement by the mouth of the subject and for communicating the interior of the mouthpiece with the airway of the subject; a medicament flow path configured to place the nebulizer interface in fluid communication with the subject interface to facilitate a flow of nebulized medicament from the nebulizer interface to the subject interface and into the airway of the subject through the subject interface; an exhaust outlet; an exhaust flow path configured to place the subject interface in fluid communication with the exhaust outlet to facilitate a flow of exhaled gas from the subject interface to the exhaust outlet and out of the mouthpiece through the exhaust outlet; an inlet valve configured to communicate ambient air with the medicament flow path, wherein the inlet valve is a one-way valve that permits flow fromambient atmosphere into the medicament flow path; and an exhaust valve that controls gas flow within the exhaust flow path, wherein the outlet valve is a one-way valve that permits flow out of the exhaust outlet, characterized in that the mouthpiece further comprises a dividing structure that physically separates the medicament flow path from the exhaust flow path. a medicament flow path configured to place the nebulizer interface in fluid communication with the subject interface to facilitate a flow of nebulized medicament from the nebulizer interface to the subject interface and into the airway of the subject through the subject interface; an exhaust outlet; an exhaust flow path configured to place the subject interface in fluid communication with the exhaust outlet to facilitate a flow of exhaled gas from the subject interface to the exhaust outlet and out of the mouthpiece through the exhaust outlet; an inlet valve configured to communicate ambient air with the medicament flow path, wherein the inlet valve is a one-way valve that permits flow fromambient atmosphere into the medicament flow path; and an exhaust valve that controls gas flow within the exhaust flow path, wherein the outlet valve is a one-way valve that permits flow out of the exhaust outlet, characterized in that the mouthpiece further comprises a dividing structure that physically separates the medicament flow path from the exhaust flow path.