A portable device for infusion of liquid drugs contained in a pair of syringes into a patients body is disclosed. Said device (10 100 300) includes a body housing a driving system and arranged to receive a pair of interchangeable syringes, and said driving system includes a single electric motor (24 124 224 324) and a first and a second mechanical assembly, or a single mechanical assembly, each assembly being associated with one of the syringes or with both syringes, respectively, and being arranged to convert the rotary motion of the motor into a linear motion and to apply said linear motion to a pusher associated with the plunger (17a, 17b 117a, 117b 317a, 317b) of the respective syringe, both mechanical assemblies, or the single mechanical assembly, being operated for simultaneously causing the forward motion of the plunger in one syringe and the backward motion of the plunger in a second syringe.
