The invention is directed to a differential gear mechanism (26) for a drug delivery device with a primary drug delivery assembly (3) and a secondary drug delivery assembly (4), wherein the primary drug delivery assembly (3) comprises a primary dose dial sleeve (17) and wherein the secondary drug delivery assembly (4) comprises a secondary drive sleeve (24). The invention is also directed to a respective drug delivery device.Linvention concerne un mécanisme dengrenage différentiel (26) pour un dispositif dadministration de médicament ayant un ensemble dadministration de médicament principal (3) et un ensemble dadministration de médicament secondaire (4), lensemble dadministration de médicament principal (3) comprenant un manchon de sélection de dose principal (17), et lensemble dadministration de médicament secondaire (4) comprenant un manchon dentraînement secondaire (24). Linvention concerne également un dispositif dadministration de médicament respectif.
