In vivo release of norethindrone coupled to a biodegradable poly(alpha-amino acid) drug delivery system.

The in vivo release of norethindrone from a biodegradable steroid-polymer conjugate was studied in rats. The drug-polymer conjugate, consisting of [3H]norethindrone coupled via a 17-carbonate bond to poly-N5-(3-hydroxypropyl)-L-glutamine was administered to female rats by subcutaneous injection. The in vivo release of steroid, determined by measuring the daily radioactivity output in urine and feces, was fairly constant though it showed a gradual decrease during the 9-month study period. The data indicate that this biodegradable norethindrone-polymer conjugate is a potential candidate for the controlled delivery of norethindrone to effect long-term contraception.