Abstract: The invention concerns a device and a process for administering a liquid g preparation, in particular by infusion, by implantation or percutaneously, at a given flow rate for relatively long period of time, using a technique involving the retractation of an elastic membrane. More specifically, using this technique, said drug preparation is placed in a tubular reservoir (13) where it is subjected to the action of at least one movable wall (112, 112a). The movable wall is displaced by the pressure of a hydraulic fluid (10), the entry of which is controlled by a capillary tube (4) fed with hydraulic fluid (10) under pressure by a hydraulic accumulator subject to the thrust of a previously dilated retractable elastic membrane (8).