The device comprises a structure sized and adapted for placement in {TAIL ~ an environment} of {HEAD ~ use}, the structure comprising a poly or a poly having a repeating mer consisting of hydrocarbon radical and a symmetrical dioxycarbon unit of the general formula: ##STR1## wherein R1 is a multivalent hydrocarbon radical, R2 and R3 are hydrocarbon radicals with at least one of R2 or R3 bonded to the dioxycarbon through an oxygen covalent bond, a beneficial agent, and a surfactant erosion rate modifier 
The device comprises a structure sized and adapted for placement in { TAIL ~ an environment } of { HEAD ~ use } , the structure comprising a poly or a poly having a repeating mer consisting of hydrocarbon radical and a symmetrical dioxycarbon unit of the general formula : # # STR1 # # wherein R1 is a multivalent hydrocarbon radical , R2 and R3 are hydrocarbon radicals with at least one of R2 or R3 bonded to the dioxycarbon through an oxygen covalent bond , a beneficial agent , and a surfactant erosion rate modifier
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