Infusion of drugs

An at least partly implantable system for injecting a substance into a patient's body, comprising

• at least one infusion needle disposed at least partly within at least one housing with a tip end of the at least one infusion needle arranged for penetrating the at least one housing's outer wall, the at least one housing being adapted for implantation inside a patient's body, and
• at least one drive unit adapted for implantation inside the patient's body, the at least one drive unit being coupled to the at least one infusion needle and arranged for advancing and retracting the tip end of the at least one infusion needle so that the at least one infusion needle penetrates, upon advancement of the tip end thereof, said at least one housing's outer wall in at least one penetration area so as to allow for injecting the substance through said at least one penetration area via the at least one infusion needle,
• wherein the at least one drive unit comprises a hydraulic drive for transmitting hydraulic energy from a remote location within the patient's body to the at least one infusion needle for advancing the tip end thereof and/or for laterally displacing the tip end thereof.