The present invention relates to a medicament delivery device comprising a distal housing part (12)a proximal housing part (10)into which a multi-chamber medicament container(14)is arranged and wherein said proximal housing part is arranged to be movable in relation to said distal housing part for mixing at least two substances arranged inside said container a plunger rod (32) arranged to act on a distal stopper (34) in said medicament container, wherein a relative movement of said housing parts (10, 12) towards each other forces said distal stopper against the plunger rod in a proximal direction for mixing at least two substances arranged inside said containera drive force unit (58, 74, 76, 78) capable of forcing said plunger rod (32) in the proximal direction for subsequent delivery of medicament from said medicament containeran activation member (80)slidably arranged through said distal housing part and releasibly connected to the drive force unitwherein said device further comprises a guide shell (24) one-way rotatable arranged in said distal housing part,wherein said guide shell is provided with threads (22) arranged to cooperate with corresponding threads (20) on said proximal housing,and wherein said guide shell and said plunger rod are arranged with guide members such that they are rotationally locked but slidable in relation to each other.La présente invention a pour objet un dispositif dadministration de médicaments comprenant une partie boîtier distal (12) une partie boîtier proximal (10) dans laquelle un récipient pour médicaments à chambres multiples (14) est disposé, et ladite partie boîtier proximal étant conçue pour être mobile par rapport à ladite partie boîtier distal pour mélanger au moins deux substances disposées à lintérieur dudit récipient une tige de piston (32) conçue pour agir sur une butée distale (34) dans ledit récipient pour médicaments, un déplacement relatif desdites parties boîtier (10, 12) lune vers lautre poussant ladite butée di
