A device for drug injection has a cartridge which in turn has a reservoir and a fluid path. The fluid path carries a fluid for injection from the reservoir to the place where the patient is to be injected. The fluid path comprises a needle and the fluid path is kept sterile. A drive chain extends the needle to the injection point but is only mechanically connected to the fluid path to operate the needle the mechanical connection being such as to operate the needle while maintaining the fluid path sterility.
