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 (P) 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 , 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 for moving the first and second coupling mechanisms 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 (P) 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 , 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 for moving the first and second coupling mechanisms between their coupling state and their uncoupling state. <EOS>