Infusion device for administering a medical fluid to a patient, comprising: - a housing, - a receptacle arranged on the housing for receiving a syringe, the syringe having a barrel for containing a medical fluid and a plunger movable relative to the barrel for delivering the medical fluid out of the barrel, - a pusher device movable along a pushing direction relative to the housing for acting onto the plunger for moving the plunger relative to the barrel, - a drive mechanism for driving the pusher device, - a first coupling mechanism operative to couple the plunger to the pusher device and a second coupling mechanism operative to couple the pusher device to the drive mechanism, and - a common actuation mechanism arranged on the pusher device and comprising an actuation element for actuating the first coupling mechanism and the second coupling mechanism between a coupling state and an uncoupling state, wherein the actuation mechanism comprises a first threaded element rotatable about a rotational axis and a second threaded element movable longitudinally along the first threaded element, the second threaded element being in threaded engagement with the first threaded element wherein the actuation element is actuatable to move the second threaded element along the first threaded element, the first threaded element being operatively connected to the first and second coupling mechanisms (36, 37), characterised in that the longitudinal movement of the second threaded element along the first threaded element is translated into the rotational movement of the first threaded element, which is transferred to the first and second coupling mechanisms (36, 37) for moving the first and second coupling mechanisms (36, 37) between their coupling state and their uncoupling state. - a housing, - a receptacle arranged on the housing for receiving a syringe, the syringe having a barrel for containing a medical fluid and a plunger movable relative to the barrel for delivering the medical fluid out of the barrel, - a pusher device movable along a pushing direction relative to the housing for acting onto the plunger for moving the plunger relative to the barrel, - a drive mechanism for driving the pusher device, - a first coupling mechanism operative to couple the plunger to the pusher device and a second coupling mechanism operative to couple the pusher device to the drive mechanism, and - a common actuation mechanism arranged on the pusher device and comprising an actuation element for actuating the first coupling mechanism and the second coupling mechanism between a coupling state and an uncoupling state, wherein the actuation mechanism comprises a first threaded element rotatable about a rotational axis and a second threaded element movable longitudinally along the first threaded element, the second threaded element being in threaded engagement with the first threaded element wherein the actuation element is actuatable to move the second threaded element along the first threaded element, the first threaded element being operatively connected to the first and second coupling mechanisms (36, 37), characterised in that the longitudinal movement of the second threaded element along the first threaded element is translated into the rotational movement of the first threaded element, which is transferred to the first and second coupling mechanisms (36, 37) for moving the first and second coupling mechanisms (36, 37) between their coupling state and their uncoupling state.