The present invention relates to a monitoring unit (200) for a medicament delivery device, which monitoring unit comprises a housing (202), monitoring circuit (398) arranged in said housing (202), capable of detecting and monitoring functions of the medicament delivery device, releasable holding elements (208), which releasable holding elements (208) are designed to interact with a medicament delivery device for releasibly holding said monitoring unit (200) when attached to a medicament delivery device, characterised in locking elements (500, 508, 514) operably arranged in said monitoring unit and designed to act on said attachment mechanism, - at least one drive element (502) operably connected to said locking elements (500, 508, 514) wherein, upon activation of said monitoring unit, said at least one drive element (502) causes said locking elements (500, 508, 514) to act on said releasable holding elements (208), preventing detachment of said monitoring unit (200) from said medicament delivery device.本發明有關用於藥物輸送裝置之監視單元(200)，該監視單元包含外殼(202)；監視電路(398)，被配置在該外殼(202)中，能夠偵測及監視該藥物輸送裝置的功能；可釋放之固持元件(208)，該可釋放的固持元件(208)被設計以與藥物輸送裝置互相作用，用於當被附接至藥物輸送裝置時可釋放地固持該監視單元(200)；其特徵為鎖定元件(500、508、514)可操作地配置在該監視單元中，且被設計以作用在該附接機件上；至少一驅動元件(502)，可操作地連接至該鎖定元件(500、508、514)，其中於該監視單元之啟動時，該至少一驅動元件(502)造成該鎖定元件(500、508、514)作用在該可釋放的固持元件(208)上，防止該監視單元(200)由該藥物輸送裝置分離。
