Metabolic disposition and elimination studies of a radiolabelled biodegradable polymeric implant in the rat brain

The metabolic disposition and elimination process of the anhydride co-polymer poly[1,3-bis(p-carboxyphenoxypropane): sebacic acid] 20:80 [P(CPP:SA)20:80] implanted in the rat brain was studied. Two polymers were prepared, one with [^14C]SA and unlabelled CPP, and the other co-polymer with [¹⁴C]CPP and unlabelled SA. With these two polymers we were able to study the metabolic disposition of each monomer after polymer degradation. Polymer wafers loaded with AJ,AJ-bis(2-chloroethyl)-JV-nitrosourea or without the drug were implanted in the rat brain. For the rats implanted with the [¹⁴C]SA-labelled polymer, approximately 40% of the radioactivity was found in the expired CO₂, 10% in the urine, about 2% in the faeces and about 10% remained in the device 7d after implantation. On the other hand, only 4% of the [¹⁴C]CPP monomer was eliminated by urine and faeces during this period. The drug-loaded polymer degraded faster than the blank polymer. This study supports the theory that the polymer is a biodegradable material that can be used for the direct and specific delivery of drugs into a targeted organ and can provide continued release of drugs over a period of time. Biomaterials (1994) 15, (9) 681-688.