An adaptor 10 for fitting to the mouthpiece of a drug inhalator, such as a pressurised metered dose inhaler (pMDI), is a tube with an air flow rate indicator such as a reed 16, a flag, or an electronic transducer and associated display. The indicator serves to indicate when the air flow rate through the adaptor is at or above a predetermined minimum level suitable for the delivery of the drug to the patient； preferably this level is at least thirty litres per minute. The indicator may be positioned upstream from the point at which the dose of aerosolized drug is ejected. Preferably, the adapter is a moulded plastic tube of constant cross section. Also disclosed are inhalators with built in flow rate indicators.
