A medication infusion system may include a controller and a reservoir module including a reservoir containing medication to be delivered to an internal wound site via the controller. The controller may have a peristaltic pump driven by a motor to urge medication to flow toward the internal wound site. The controller and the reservoir module may each have a mating surface oriented such that the reservoir module can slide into engagement with the controller along a direction parallel to an axis of rotation of the motor. The mating surfaces may have features such as dovetails that facilitate secure assembly and retention. A reservoir module may include only a single reservoir for infusion, or two separate reservoirs for infusion and aspiration. One single controller may be capable of mating with either type of reservoir module to provide only infusion, or infusion combined with aspiration, as desired.