An actuator for an inhaler for delivering drug by inhalation, comprising: a housing (11; 111 ) for receiving a canister (5; 106) which comprises a body (7; 107) which includes a base and a head and defines a chamber for containing drug, and a valve stem (8; 108) which extends from the body (7; 107) and from which drug is in use delivered on actuation of the canister (5; 106); an outlet (13; 105) through which a user in use inhales; and a nozzle (4; 104) which provides for delivery of drug through the outlet (13; 105); wherein at least a rear section of the outlet (13; 105) has an increasing internal dimension in a direction away from the nozzle (4; 104).