A nebulizer comprising: a container for containing fluid, a reservoir in fluid communication with the container, an aerosol generator in fluid communication with the reservoir and situated to eject fluid from the reservoir as an aerosol, a dose selection mechanism permitting a user to select an amount of fluid to be moved from the container into the reservoir, and a titration mechanism comprising: a plunger moveably mounted in the nebulizer and situated to act upon the container and an actuator moveably mounted on the nebulizer wherein operation of the actuator by a user causes the selected amount of fluid to be moved from the container into the reservoir; characterized in that: the container comprises a collar having a tab; the reservoir comprises a detent that interlocks with the tab to hold the container and reservoir together; the titration mechanism comprises a screw assembly mechanically engaged with the plunger, a dose selection mechanism mechanically engaged with the screw assembly to permit a user to select an amount of fluid to be moved from the container into the reservoir, and an actuator moveably mounted on the nebulizer to act upon the screw assembly to cause linear movement of the plunger; wherein operation of the dose selection mechanism selectively sets the linear distance the plunger will be caused to move when the actuator is operated, wherein movement of the plunger causes the plunger to act upon the container in such a manner so as to cause the selected amount of fluid to be moved from the container into the reservoir. a container for containing fluid, a reservoir in fluid communication with the container, an aerosol generator in fluid communication with the reservoir and situated to eject fluid from the reservoir as an aerosol, a dose selection mechanism permitting a user to select an amount of fluid to be moved from the container into the reservoir, and a titration mechanism comprising: a plunger moveably mounted in the nebulizer and situated to act upon the container and an actuator moveably mounted on the nebulizer wherein operation of the actuator by a user causes the selected amount of fluid to be moved from the container into the reservoir; characterized in that: the container comprises a collar having a tab; the reservoir comprises a detent that interlocks with the tab to hold the container and reservoir together; the titration mechanism comprises a screw assembly mechanically engaged with the plunger, a dose selection mechanism mechanically engaged with the screw assembly to permit a user to select an amount of fluid to be moved from the container into the reservoir, and an actuator moveably mounted on the nebulizer to act upon the screw assembly to cause linear movement of the plunger; wherein operation of the dose selection mechanism selectively sets the linear distance the plunger will be caused to move when the actuator is operated, wherein movement of the plunger causes the plunger to act upon the container in such a manner so as to cause the selected amount of fluid to be moved from the container into the reservoir. the container comprises a collar having a tab; the reservoir comprises a detent that interlocks with the tab to hold the container and reservoir together; the titration mechanism comprises a screw assembly mechanically engaged with the plunger, a dose selection mechanism mechanically engaged with the screw assembly to permit a user to select an amount of fluid to be moved from the container into the reservoir, and an actuator moveably mounted on the nebulizer to act upon the screw assembly to cause linear movement of the plunger; wherein operation of the dose selection mechanism selectively sets the linear distance the plunger will be caused to move when the actuator is operated, wherein movement of the plunger causes the plunger to act upon the container in such a manner so as to cause the selected amount of fluid to be moved from the container into the reservoir.