A pre-filled injection device for apportioning set doses of a liquid drug comprising: A pen-shaped housing extending in a longitudinal direction and having a needle supporting distal end, A removable protective cap mountable on the housing and covering at least a part of the needle supporting distal end between injections, and which removable protective cap is rotatable relatively to the housing when mounted there upon, A non-replaceable cartridge permanently embedded in the housing of the pre-filled injection device and having an interior containing the liquid drug, A needle assembly comprising a needle cannula secured in a hub which needle cannula has a distal end with a distal tip and a proximal end and wherein the proximal end of the needle cannula is inserted into the cartridge , A telescopically movable shield movable from an extended position covering at least the distal tip of the needle cannula to a retracted position and which telescopically movable shield carries a cleaning chamber for cleaning at least the distal tip of the needle cannula between subsequent injections, and which telescopically movable shield is rotatable mounted relatively to the housing , characterised in that the cleaning chamber contains an amount of the same liquid drug as contained in the cartridge , wherein the removable protecting cap when mounted engages the telescopically movable shield such that rotation of the protective cap relatively to the housing is transformed to a rotation of the telescopically movable shield , and wherein the telescopically movable shield is arranged such that the rotation of the telescopically movable shield moves the telescopically movable shield in the proximal direction to a position in which the distal tip of the needle cannula is located in front of the cleaning chamber carried by the telescopically movable shield . A pen-shaped housing extending in a longitudinal direction and having a needle supporting distal end, A removable protective cap mountable on the housing and covering at least a part of the needle supporting distal end between injections, and which removable protective cap is rotatable relatively to the housing when mounted there upon, A non-replaceable cartridge permanently embedded in the housing of the pre-filled injection device and having an interior containing the liquid drug, A needle assembly comprising a needle cannula secured in a hub which needle cannula has a distal end with a distal tip and a proximal end and wherein the proximal end of the needle cannula is inserted into the cartridge , A telescopically movable shield movable from an extended position covering at least the distal tip of the needle cannula to a retracted position and which telescopically movable shield carries a cleaning chamber for cleaning at least the distal tip of the needle cannula between subsequent injections, and which telescopically movable shield is rotatable mounted relatively to the housing , characterised in that the cleaning chamber contains an amount of the same liquid drug as contained in the cartridge , wherein the removable protecting cap when mounted engages the telescopically movable shield such that rotation of the protective cap relatively to the housing is transformed to a rotation of the telescopically movable shield , and wherein the telescopically movable shield is arranged such that the rotation of the telescopically movable shield moves the telescopically movable shield in the proximal direction to a position in which the distal tip of the needle cannula is located in front of the cleaning chamber carried by the telescopically movable shield . <EOS>