An aerosol drug delivery apparatus, comprising: a reservoir constructed to contain a predetermined dose of a liquid drug; an aerosol generator in communication with the reservoir; a power source arranged to deliver power to the aerosol generator, the powered aerosol generator producing an aerosolized form of the dose that can be administered to a patient; characterized in that said aerosol drug delivery apparatus further comprises: a breath measuring mechanism configured to monitor the patient's breathing pattern during the administration of the dose; wherein the breath measuring mechanism includes a sensor configured to measure a ratio of the patient's inhalation with respect to exhalation; a data repository storing settings that describe a treatment to be administered: and at least one controller configured to control the power source, the controller configured to vary the power level at which the power source operates during the administration of the dose based on the monitored breathing pattern, wherein the controller is configured to vary a level of power delivered to the aerosol generator, wherein the settings stored in the data repository include information relating to power levels; and wherein, the controller is configured to vary the power level by increasing the power level when the ratio falls below a predetermined threshold, and/or wherein, the controller is configured to vary the power level by decreasing the power level when the ratio exceeds a predetermined threshold. a reservoir constructed to contain a predetermined dose of a liquid drug; an aerosol generator in communication with the reservoir; a power source arranged to deliver power to the aerosol generator, the powered aerosol generator producing an aerosolized form of the dose that can be administered to a patient; characterized in that said aerosol drug delivery apparatus further comprises: a breath measuring mechanism configured to monitor the patient's breathing pattern during the administration of the dose; wherein the breath measuring mechanism includes a sensor configured to measure a ratio of the patient's inhalation with respect to exhalation; a data repository storing settings that describe a treatment to be administered: and at least one controller configured to control the power source, the controller configured to vary the power level at which the power source operates during the administration of the dose based on the monitored breathing pattern, wherein the controller is configured to vary a level of power delivered to the aerosol generator, wherein the settings stored in the data repository include information relating to power levels; and wherein, the controller is configured to vary the power level by increasing the power level when the ratio falls below a predetermined threshold, and/or wherein, the controller is configured to vary the power level by decreasing the power level when the ratio exceeds a predetermined threshold. a breath measuring mechanism configured to monitor the patient's breathing pattern during the administration of the dose; wherein the breath measuring mechanism includes a sensor configured to measure a ratio of the patient's inhalation with respect to exhalation; a data repository storing settings that describe a treatment to be administered: and at least one controller configured to control the power source, the controller configured to vary the power level at which the power source operates during the administration of the dose based on the monitored breathing pattern, wherein the controller is configured to vary a level of power delivered to the aerosol generator, wherein the settings stored in the data repository include information relating to power levels; and wherein, the controller is configured to vary the power level by increasing the power level when the ratio falls below a predetermined threshold, and/or wherein, the controller is configured to vary the power level by decreasing the power level when the ratio exceeds a predetermined threshold.