The present disclosure relates to a administration assembly for a medicament delivery device, comprising: an elongated tubular delivery member cover (7), a cartridge holder (11) configured to be received by the delivery member cover (7) and configured to accommodate a medicament cartridge (31), the cartridge holder (11) having a radially flexible and radially inwards extending cartridge blocking protrusion (11b) configured to prevent the medicament cartridge (31) from moving proximally until being subjected to a proximally directed force larger than a threshold value, a needle assembly (13) comprising a double-edged needle having a proximally extending needle portion (13a) and a distally extending needle portion (13b), wherein the needle assembly (13) is configured to be assembled with the cartridge holder (11) so that the distally extending needle portion (13b) extends into the cartridge holder (11), and an administration mechanism including a plunger rod (27) configured to be proximally biased, wherein the delivery member cover (7) is configured to be linearly displaced in the distal direction relative to the cartridge holder (11), and wherein the delivery member cover (7) is configured to activate the administration mechanism when moved in the distal direction, causing the administration mechanism to move the cartridge holder (11) in the proximal direction and to subsequently move the plunger rod (27) in the proximal direction inside the cartridge holder (11) with a force larger than athe threshold value.
