A nebulizer which has an insertable container and a counter device for counting operations of the nebulizer, and is opened for replacing the container. A securing device having locking portions which are forced apart is provided to prevent reconnection of an already used container. The nebulizer has an indicator for showing the current container number and/or symbols indicating the need container replacement. The indicator is driven by the force of an internal spring. The indicator member also controls a lock of the container for locking the container against further actuation. The lock is reset after container replacement.