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