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