METHOD OF MANUFACTURING PREFILLED DRUG DELIVERY DEVICES

The present invention provides a method of manufacturing a prefilled drug delivery device comprising the steps of arranging a piston rod member (20, 22, 120, 122) and a piston rod guide (40, 140) in a housing (10, 110) such that the piston rod member extends through a guide structure (13, 113) fixed in the housing and is surrounded by and operatively coupled with the piston rod guide, whereby rotation of the piston rod guide in a first direction relative to the housing causes distal movement of the piston rod member relative to the guide structure, and vice versa, and rotation of the piston rod guide in a second direction relative to the housing causes proximal movement of the piston rod member relative to the guide structure, and vice versa, and the piston rod guide is in a first state being capable of bi-directional rotation with respect to the housing, bringing a displaceable wall (62, 162) of a variable volume drug reservoir (60, 160) into abutment with a distal end portion of the piston rod member, moving the variable volume drug reservoir proximally relative to the housing to a completely mounted position, and shifting the piston rod guide irreversibly to a second state in which rotation of the piston rod guide in the second direction relative to the housing is prevented.