Some embodiments relate to a method for providing, during a single inhalation from an inhaler, a controllable ratio between at least a first active substance and a second active substance provided from the same source material, comprising: defining a ratio between the first and second active substances to be delivered to a user； setting operation parameters in accordance with the ratio, the operation parameters including at least one of a heating profile of the source material and an airflow profile through the source material； and operating the inhaler according to the operation parameters to deliver to the user, during a single inhalation, at least the first and second active substances at the defined ratio.
