Effect of drug-vinyl copolymer delivery composites on the rat prostate

Administration of human chorionic gonadotropin with a controlled-release function to immature rats for application in male infertility therapy

Biodegradable poly(DL-lactic acid) (PLA) devices with controlled release of human chorionic gonadotropin (hCG) were fabricated in a 2-mm cylinder form by the meltpressing technique. The devices fabricated were inserted subcutaneously in the backs of immature rats. It was found that the serum level of testosterone (T) remained constant at approximately 0.7 ng/ml for an experimental period of 14 days, resulting in greater Leydig cell production of testosterone. This was also suggested from the results of immunohistochemical observation of the testis and weight changes of prostates, such as the ventral prostates and seminal vesicle.

In vivo characteristics of injectable poly(DL-lactic acid) microspheres for long-acting drug delivery

Poly(DL-lactic acid) (PLA) microspheres containing testosterone (T) were prepared by the solvent evaporation process to evaluate their physical properties such as size distribution, shape, drug content, in vivo controlled drug release, pharmacological influences on the prostate gland in castrated rats, and histopathological findings of tissues surrounding the implants. The in vivo release of T from PLA microspheres containing 30 mg of drug obtained with chloroform was continued over a 6-week period. This effect is attributed to high dispersibility of T in the device when obtained with chloroform. Both serum drug levels and prostate gland weight recovery suggested the effects of a long-acting drug delivery system. The histopathological findings showed that the devices used were completely degraded 10 weeks after injection.

Sequential polydepsipeptides as biodegradable carriers for drug delivery systems

Sequential polydepsipeptides containing both peptide and ester bonds, poly[(L-alanyl)n-gamma-ethyl L-glutamyl-L-lactyl] (n = 0, 1, 2, and 3) (poly[(Ala)n-Glu(OEt)-Lac]), were prepared for application as biodegradable carriers for drug delivery systems. The in vivo degradation of these polymers was evaluated by subcutaneous implantation in the backs of male rats, and was strongly influenced by the number (n) of Ala units in poly[(Ala)n-Glu(OEt)-Lac]. The resulting poly(Ala-Ala-Glu(OEt)-Lac) gave the highest degradability, in which 100% degradation was observed 24 weeks from the start of implantation. A luteinizing-hormone-releasing hormone agonist des-Gly10-[D-Leu6]-LH-RH ethylamide (LH-RH agonist), was incorporated into a sequential poly(Ala-Ala-Glu(OEt)-Lac) carrier by the melt-pressing technique, which gave fine cylindrical polymer formulations with different structures of drug dispersion, e.g., blend-type and sandwich-type formulations. The rate of in vivo release of LH-RH agonist from a blend-type formulation showed a linear decrease with time until its release was finished after 6 weeks' implantation. In contrast, in a sandwich-type formulation, the in vivo release rate was apparently maintained constant over a period of 16 weeks (24 +/- 14 micrograms/day).