Subcutaneous testosterone transport characteristics in castrated Wister rats with controlled drug delivery composites containing poly(ethylene glycol)(Msub(n)=1900-2100)

The radiation polymerized testosterone-vinyl ester copolymer delivery composites containing poly(ethylene glycol)(Msub(n)=1900-2100) as a transportable promoter were implanted subcutaneously in castrated Wistar rats over a period of at most 90 days. The in vivo cumulative amounts of testosterone released from the above composite on the 7th, 30th, and 90th day from implantation were 498, 2120, and 6913μg, respectively. These values were about 3.2 times larger than those released in vivo from the composites containing no poly(ethylene glycol). The comparison of in vitro and in vivo cumulative amounts of testosterone released from polyethylene glycol-containing composites showed that the in vivo cumulative amount of released drug was about 2 times larger than that in vitro. It was concluded from these results that poly(ethylene glycol) effectively acted as a drug-transportable promoter when the composite was implanted subcutaneously in rats. This is also suggested from the results of serum testosterone concentration and physiological response (as a measure of changes in weight of the ventral prostates) in castrated rats with drug delivery composites. (author)