A drug delivery device is provided comprising a drug reservoir chamber (16) containing a substance to be delivered in fluid connection with a drug administration means, and a control cell (10) that is constituted by an electrochemical cell comprising electrodes (12), an electrolyte (13) and a housing surrounding the electrodes, wherein a part of the housing is a displaceable wall that couples the electrochemical cell to the drug reservoir chamber, wherein when the electrochemical cell discharges, a volume change occurs in the electrochemical cell, said volume change being conveyed by said displaceable wall to said drug reservoir chamber such that said substance is expelled from said drug chamber towards said drug administration means.
