A metered dose inhaler for dispensing aerosol doses comprising: an actuation housing, and a canister containing an aerosol and having a valve located at a valve end thereof, wherein the canister is received in the actuation housing and is configured to move in a longitudinal direction from a rest position to an activation position in which the valve is depressed against a bottom portion of the actuation housing such that an aerosol dose is released, a triggering unit with a single trigger member provided on a flexible member or formed by a flexible member, wherein the flexible member is configured to interact with the canister and to be moved by the canister in a lateral direction transverse to the longitudinal direction when the canister moves in the longitudinal direction from the rest position to the activation position, a circuit assembly having a substrate with a switch thereon, the switch being configured to interact with the trigger member such that the trigger member triggers the switch when the canister moves from the rest position to the activation position, wherein a) the flexible member is arranged such that after a predetermined displacement of the canister from the rest position into an intermediate position between the rest position and the activation position of the canister, the canister interacts with the flexible member so that the trigger member triggers the switch when the canister reaches the intermediate position, and wherein displacement from the intermediate position to the actuation position causes displacement of the valve so that an aerosol dose is released, or wherein b) the flexible member is arranged such that the trigger member triggers the switch when the canister reaches the activation position characterized in that the triggering unit comprises a body portion that is positioned in the actuation housing between a wall of the actuation housing and the canister, wherein the circuit assembly is attached to the body portion, that the body portion comprises a plate that extends in longitudinal direction, that the flexible member is attached to the body portion and extends in longitudinal direction so that the trigger member is resiliently pivotable in the lateral direction with respect to the body portion and, that the flexible member is formed as a flexible tongue that extends from the body portion of the triggering unit in longitudinal direction, wherein at least a part of the flexible tongue extends toward the canister. an actuation housing, and a canister containing an aerosol and having a valve located at a valve end thereof, wherein the canister is received in the actuation housing and is configured to move in a longitudinal direction from a rest position to an activation position in which the valve is depressed against a bottom portion of the actuation housing such that an aerosol dose is released, a triggering unit with a single trigger member provided on a flexible member or formed by a flexible member, wherein the flexible member is configured to interact with the canister and to be moved by the canister in a lateral direction transverse to the longitudinal direction when the canister moves in the longitudinal direction from the rest position to the activation position, a circuit assembly having a substrate with a switch thereon, the switch being configured to interact with the trigger member such that the trigger member triggers the switch when the canister moves from the rest position to the activation position, wherein a) the flexible member is arranged such that after a predetermined displacement of the canister from the rest position into an intermediate position between the rest position and the activation position of the canister, the canister interacts with the flexible member so that the trigger member triggers the switch when the canister reaches the intermediate position, and wherein displacement from the intermediate position to the actuation position causes displacement of the valve so that an aerosol dose is released, or wherein b) the flexible member is arranged such that the trigger member triggers the switch when the canister reaches the activation position a) the flexible member is arranged such that after a predetermined displacement of the canister from the rest position into an intermediate position between the rest position and the activation position of the canister, the canister interacts with the flexible member so that the trigger member triggers the switch when the canister reaches the intermediate position, and wherein displacement from the intermediate position to the actuation position causes displacement of the valve so that an aerosol dose is released, or wherein b) the flexible member is arranged such that the trigger member triggers the switch when the canister reaches the activation position characterized in that the triggering unit comprises a body portion that is positioned in the actuation housing between a wall of the actuation housing and the canister, wherein the circuit assembly is attached to the body portion, that the body portion comprises a plate that extends in longitudinal direction, that the flexible member is attached to the body portion and extends in longitudinal direction so that the trigger member is resiliently pivotable in the lateral direction with respect to the body portion and, that the flexible member is formed as a flexible tongue that extends from the body portion of the triggering unit in longitudinal direction, wherein at least a part of the flexible tongue extends toward the canister.