The present invention provides a drug delivery device (2, 3 102) for sequential administration of substances, comprising a first variable volume reservoir (40a 140a) holding a first substance and comprising a first outlet (41 a, 141 a) and a first displaceable wall (43a 143a), a second variable volume reservoir (40b 140b) holding a second substance and comprising a second outlet (41 b 141 b) and a second displaceable wall (43b 143b), a first wall actuation structure (65a, 70a, 75a, 77a 177a) activatable to move the first displaceable wall (43a 143a) and thereby expel a dose of the first substance through the first outlet (41 a 141 a), a second wall actuation structure (65b, 70b, 75b, 77b 177b) activatable to move the second displaceable wall (43b 143b) and thereby expel a dose of the second substance through the second outlet (41 b 141 b), and a drive structure (90 190) for activating the first wall actuation structure (65a, 70a, 75a, 77a 177a) and the second wall actuation structure (65b, 70b, 75b, 77b 177b). The drive structure (90 190) performs a predetermined movement during one sequential administration of the first substance and the second substance, the prede- termined movement comprising a first part movement followed by a second part movement, and is configured to activate the first wall actuation structure (65a, 70a, 75a, 77a 177a) during the first part movement and to activate the second wall actuation structure (65b, 70b, 75b, 77b 177b) during the second part movement.La présente invention concerne un dispositif dadministration de médicament (2, 3 102) pour ladministration séquentielle de substances, comprenant un premier réservoir à volume variable (40a 140a) contenant une première substance et comprenant une première sortie (41 a, 141a) et une première paroi mobile (43a 143a), un deuxième réservoir à volume variable (40b 140b) contenant une deuxième substance et comprenant une deuxième sortie (41b 141b) et une deuxième paroi mobile (43b 143b), une
