Mechanism for reducing risk of drug contamination

Abstract

The present invention provides a drug delivery system () comprising a drug delivery device () carrying at least one reservoir (), and a needle unit () being attachable to the drug delivery device () in axial extension thereof and adapted to establish a flow way between the at least one reservoir () and a drug delivery site. The needle unit () comprises a needle structure () comprising a front needle portion () for entering the drug delivery site, and at least one back needle portion () for insertion into the at least one reservoir (), and a needle shield (). The needle shield () and the needle structure () are capable of undergoing relative axial motion between an accommodating relative position in which the needle structure () is completely accommodated within the needle shield () and a protruding relative position in which the front needle portion () protrudes from the needle shield (), the needle shield () and the needle structure () being biased towards the accommodating relative position by a first bias force. When the needle unit () is attached to the drug delivery device () the needle structure () and the at least one reservoir () are capable of undergoing relative axial motion between a disconnected relative position in which the at least one back needle portion () is spaced apart from the at least one reservoir (), and a connected relative position in which the at least one back needle portion () and the at least one reservoir () are fluidly connected, the needle structure () and the at least one reservoir () being biased towards the disconnected relative position by a second bias force which is greater than the first bias force.