A dispenser (FIG. 1, 1) comprises a reservoir (10) of a physiologically active substance and a droplet ejection device (14), for example a bubble jet or pizeoelectric device, which is controlled to issue a predetermined number of discrete droplets of the substance from ejection orifices (15) upon actuation. Device (14) may be actuated by a pressure transducer (19) responsive to inhalation and issue the droplets into an airstream (A) which enters at slot (7) and is then inhaled via mouthpiece (5). In other embodiments (FIG. 5) the dispenser is finger actuated and directed by hand for topical application. The number and/or frequency of droplets issued is programmatically controlled by a control circuit (16) whereby average and total dose of the substance are predetermined.