Studies on the In Vitro and In Vivo Release of Hormonal Steroids Bound to a Polymer Base

Abstract

Poly (ethylene) glycol (PEG) based hydrogels crosslinked with 1,1,1, tris (hydroxy methyl) ethane, in phase separated hydrogcls and 1,2,6, hexane triol in non-phase ·separated hydrogels were used to study the characteristics of release of hormonal steroids testosterone, progesterone and estradiol. A rapid in vitro release of steroids was observed with lM PEG-6000 non-phase separated gel. A dramatic slowing down in the in vitro release characteristics was observed in the case of phase-separated gels and with increasing crosslinking. The time for 50% release (t0.s) for the steroids was of the order of 9.Sh, 10.Sh and 12h for 1.5M, 2M and 3M PEG-6000 hydrogels, respectively. The 3M PEG-6000 phase separated gels retained the same characteristics of release in vivo since only 2.0% of 3H-progesterone was released by 72h. The data demonstrates that PEG based hydrogels with appropriate crosslinking can be used effectively for sustained release of steroids from the site of implantation.