Release of 5-fluorouracil by biodegradable poly(ester-ether-ester)s. Part I: release by fused thin sheets

The 5-fluorouracil release by biodegradable epsilon-caprolactone and L-lactide copoly(ester-ether-ester)s was tested. The drug-copolymer mixture was formed by fusion in thin sheets, which were dipped in Dulbecco's PBS for time intervals ranging from one hour to two months. Each experiment shows a fast initial release, which subsequently slows down and stops at a limiting value, depending on the copolymer composition. This behavior was attributed to an extraction of the drug present on the sheet surface, due only to its shape, and to hydrogen bonds between the drug and the copolymers. The results obtained lead to a possibility of using such copolymers as "time-delayed" drug-releasing systems, when formed in specimens with smaller surface-to-volume ratio, which could minimize the fast initial extraction.