Controlled release of human growth hormone in rats following parenteral administration of poloxamer gels

The use of poloxamer-407 to develop a sustained release formulation of recombinant human growth hormone (rhGH) was evaluated. Since poloxamer 407 undergoes reverse thermal gelation, it can be injected as a solution but then it forms a gel matrix at body temperature. In vitro release studies were conducted at 37 degrees C for 72 h. An approximate zero order release profile was observed as measured by HPLC assay. lodination of rhGH was then performed for the release of I-125-rhGH from poloxamer gel. In vivo studies in rats were then conducted using the poloxamer gel formulation for controlled release of rhGH following administration by intramuscular and subcutaneous routes. The controlled release formulation continued to release rhGH in vitro for 60-72 h and for a week in vivo following intramuscular and subcutaneous injections. Controlled release of rhGH was observed following administration by either route, but no significant difference (P<0.05) was observed between these routes. (C) 1997 Elsevier Science B.V.