In another embodiment the drug pump can include several valves, {HEAD ~ each valve} being in communication with one of the reservoirs and in fluid communication with {TAIL ~ the outlet port} 
In another embodiment the drug pump can include several valves , { HEAD ~ each valve } being in communication with one of the reservoirs and in fluid communication with { TAIL ~ the outlet port }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL