Patent ID: 8216177

Claim:
A drug delivery system comprising: an implantable pump assembly; two or more implantable reservoirs operably connected to the implantable pump assembly; a catheter connection port adapted to attach a catheter to the drug delivery system; a reservoir switching valve assembly between the two or more implantable reservoirs and the catheter connection port via the reservoir valve switching assembly, wherein the two or more implantable reservoirs can be selectively connected to the catheter connection port, and wherein two reservoirs of the two or more reservoirs contain fluids having different densities; an implantable density sensor configured to sense density of cerebrospinal fluid of a patient in which the sensor is implanted; and a controller operably coupled to the reservoir switching valve assembly and to the implantable density sensor, wherein the controller is configured to cause the reservoir switching valve assembly to alternate between (i) selectively coupling one or more of the two or more reservoirs to the catheter connection port to cause a fluid that is hypobaric relative to the density of the cerebrospinal fluid to be delivered to the catheter connection port, and (ii) selectively coupling a different one or more of the two or more reservoirs to the catheter connection port to cause a fluid that is hyperbaric relative to the density of the cerebrospinal fluid to be delivered to the catheter connection port.