A continuous pump relay system comprising: a plurality of drivers comprising a first and a second driver (22, 23, 48, 50) having forward and reverse directions, wherein the first and second drivers are configured to discharge fluid from a plurality of medication containers comprising a first and a second medication container (24, 26), respectively, when operating in the forward direction; a fluid communication device including a plurality of fluid inputs comprising a first and a second fluid input configured to receive fluid from the first and second medication containers (24, 26), and a fluid output having a reflux barrier which functions as a one-way valve and is configured to open and allow fluid in the fluid communication device to flow through the reflux barrier when a pressure is equal to or higher than a cracking pressure of the reflux barrier; a pressure sensing device comprising one or more sensors configured to generate sensor signals representative of fluid pressure at one or more locations within the fluid communication device; and a controller coupled to the first and second drivers (22, 23) and the pressure sensing device; the continuous pump relay system being characterized in that the controller is configured to operate the first and second drivers (22, 23) based at least on the sensor signals so as to changeover the system from delivering fluid from the first medication container at a reference pressure to delivering fluid from the second medication container by operating the first driver in the reverse direction to decrease the fluid pressure to a pressure below the cracking pressure of the reflux barrier and then stopping the first driver, and then operating the second driver in the forward direction at a first rate until the fluid pressure reaches a predetermined fraction of the reference pressure and then at a second rate, less than the first rate, until the fluid pressure reaches the reference pressure without creating a bolus. a plurality of drivers comprising a first and a second driver (22, 23, 48, 50) having forward and reverse directions, wherein the first and second drivers are configured to discharge fluid from a plurality of medication containers comprising a first and a second medication container (24, 26), respectively, when operating in the forward direction; a fluid communication device including a plurality of fluid inputs comprising a first and a second fluid input configured to receive fluid from the first and second medication containers (24, 26), and a fluid output having a reflux barrier which functions as a one-way valve and is configured to open and allow fluid in the fluid communication device to flow through the reflux barrier when a pressure is equal to or higher than a cracking pressure of the reflux barrier; a pressure sensing device comprising one or more sensors configured to generate sensor signals representative of fluid pressure at one or more locations within the fluid communication device; and a controller coupled to the first and second drivers (22, 23) and the pressure sensing device; the continuous pump relay system being characterized in that the controller is configured to operate the first and second drivers (22, 23) based at least on the sensor signals so as to changeover the system from delivering fluid from the first medication container at a reference pressure to delivering fluid from the second medication container by operating the first driver in the reverse direction to decrease the fluid pressure to a pressure below the cracking pressure of the reflux barrier and then stopping the first driver, and then operating the second driver in the forward direction at a first rate until the fluid pressure reaches a predetermined fraction of the reference pressure and then at a second rate, less than the first rate, until the fluid pressure reaches the reference pressure without creating a bolus.