Pen-type injector

A drug delivery device comprising:

• a housing comprising a dose dispensing end and a first thread;
• a dose indicator comprising a second thread that engages with the first thread;
• a driving member comprising a third thread;
• a sleeve that is (i) disposed between the dose indicator and the driving member and (ii) releasably connected to the dose indicator;
• a piston rod comprising either an internal or an external fourth thread that is engaged with the third thread;
• a piston rod holder that is rotatably fixed relative to the housing and configured to (i) prevent the piston rod from rotating during dose setting and (ii) permit the piston rod to traverse axially towards the distal end during dose dispensing;
• wherein:
• the housing is disposed at an outermost position of the drug delivery device;
• the dose indicator is disposed between the housing and the sleeve and is configured to (i) rotate and traverse axially away from the dose dispensing end during dose setting and (ii) rotate and traverse axially towards the dose dispensing end during dose dispensing;
• the driving member is configured to rotate relative to the piston rod;
• the sleeve is rotatably fixed relative to the driving member and configured to traverse axially with the dose indicator;
• and
• the piston rod and the driving member are configured to rotate relative to one another during dose dispensing;
• and the piston rod is configured to traverse axially towards the dose dispensing end during dose dispensing.