The present invention provides a drug delivery device comprising a drug reservoir chamber (15) containing a substance (16) to be delivered in fluid connection with a drug administration means (17) and (18), and a hydraulic control chamber (9) containing an electrically controlled, non-gassing, volume changing means (13), a coupling means (14) coupling said hydraulic control chamber (9) to said drug chamber (15), the arrangement being such that a change in the electrical control means (11) causes a change in the volume of the volume changing means (13), the volume change being conveyed by the coupling means (14) to the drug chamber (15) such that the substance (16) is expelled from the drug chamber (15) towards the drug administration means (17) and (18).
