MEDICATION STORAGE AND DISTRIBUTION SYSTEM

The medication storage and distribution system, as shown in Figure 4, consists of a micropump connected to a set of reservoirs controlled by electrically activated valves. The pump is actuated when one of the valves is activated in order to deliver medication to the tumor site via the circulation catheter. In our design, we have considered 1) complete sealing to prevent contamination, 2) a technique to withdraw the contents without creating vacuum, 3) a refilling mechanism, and 4) a sufficient size in order to reduce the number of refills. We have identified the use of metal bellows style reservoirs (Figure 6) as a method that meets our specifications. These reservoirs are currently available off-the-shelf or in custom versions and are currently used in implantable infusion pumps (e.g., Medtronic Synchromed and Codman implantable pumps). The reservoirs use an inert gas propellant to solve the pressure difference caused by the loss of contents (Figure 5). The titanium (or stainless steel) construction prevents the medications contained from being contaminated.

Many implantable pumps have a single self-sealing septum that can be accessed with a needle to replenish the medication. A dual septum system is also available for those who are extremely concerned with contamination. We will utilize a refilling mechanism using a dual septum coupled with a micro filter in order to reduce the risk of contamination. 

In our design, a single pump is used to withdraw medication from several reservoirs in order to reduce size (as the pumps are several orders of magnitude larger than valves) and improve calibration of pump rate. Electrically-activated piezoelectric valves are used to select the individual reservoirs. We plan to rigorously test the pumps, valves and reservoirs to calibrate as well as validate the reliability in order to meet regulatory requirements.