An infusion device for a drug delivery system comprises an infusion needle (1)having a tip end (2) and a drive unit (D) coupled to the infusion needle and arrangedfor advancing the tip end of the infusion needle to penetrate any fibrosis whenthe infusion device is implanted in a patient's body. The infusion needleand drive unit are designed for implantation in a patient's body. Othercomponents of the drug delivery system may be part of the implantable infusiondevice or, alternatively, be for extracorporal use cooperating with the implantedinfusion device. Preferably, the infusion needle can be advanced and retractedwith each infusion cycle. Furthermore, upon each advancement and/or retraction,the needle may be moved laterally so as to vary the injection site. Needle (1 ) anddrive unit (D) are preferably disposed within a body (15), with the infusion needlebeing arranged for penetrating a self-sealing penetration membrane (18).
