An adapter for fitting to a drug delivery device, the adapter including: an outlet for communication with the mouth of a patient; an air flow path through the adapter along which air is drawn to the outlet by inhalation by the patient; an inlet adapted for connection to a mouthpiece of the drug delivery device; and an air flow rate indicator operable to indicate when the air flow rate along the air flow path is at or above a predetermined minimum level suitable for delivery of the drug to the patient. A drug delivery device having, in its body, an air flow rate indicator operable to indicate when the air flow rate along the air flow path is at or above a predetermined minimum level suitable for delivery of the drug to the patient.