A beneficial agent present in the devices is released at a controlled rate and in {HEAD ~ effective amounts} as {TAIL ~ the polymers} erode over time 
as
A beneficial agent present in the devices is released at a controlled rate and in { HEAD ~ effective amounts } as { TAIL ~ the polymers } erode over time
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH