A portable device for infusion of liquid drugs contained in a pair of syringes into a patients body is disclosed. Said device 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 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 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.
