Claims for Patent: 5,989,581

Summary for Patent: 5,989,581

Title:	Drug delivery system for two or more active substances
Abstract:	The present invention is dealing with a drug delivery system, preferably in a ring-shaped form suitable for vaginal administration, for the simultaneous release of a progestogenic steroid compound and an estrogenic steroid compound in a fixed physiological ratio over a prolonged period of time. The drug delivery system comprises at least one compartment comprising a thermoplastic polymer core containing the mixture of the progestogenic and estrogenic compounds and a thermoplastic polymer skin, the progestogenic compound being initially dissolved in the polymer core material in a relatively low degree of supersaturation.
Inventor(s):	Groenewegen; Rudolf Johannes Joseph (Heesch, NL)
Assignee:	Akzo Nobel N.V. (Arnhem, NL)
Application Number:	09/056,700
Patent Claims:	1. A drug delivery system comprising at least one compartment which comprises a thermoplastic polymer core and a thermoplastic polymer skin covering the core, said core comprising a mixture of a steroidal progestogenic compound and a steroidal estrogenic compound in a ratio by weight that allows a direct release of both said progestogenic compound and said estrogenic compound in physiologically required amounts, said progestogenic compound being initially dissolved in said polymer core material in a degree of supersaturation of 1 to about 6 times of the amount by weight necessary for obtaining saturation concentration of said progestogenic compound in said polymer core material at 25.degree. C., said estrogenic compound being dissolved in said polymer core material in a concentration lower than that of said progestogenic compound, and said thermoplastic skin being permeable for said progestogenic and estrogenic compounds. 2. A drug delivery system according to claim 1, wherein the delivery system has a substantially ring-shaped form and is intended for vaginal administration of the mixture of the progestogenic and estrogenic compounds. 3. A drug delivery system according to claim 1, wherein at least the skin material comprises ethylene-vinylacetate copolymer as the thermoplastic polymer. 4. A drug delivery system according to claim 1, wherein the amount of progestogenic compound dissolved in the thermoplastic core material is 2 to 5 times the amount necessary for obtaining saturation concentration. 5. A drug delivery system in a substantially ring-shaped form and suitable for vaginal administration comprising at least one compartment which comprises a thermoplastic polymer core and a thermoplastic polymer skin covering said core, said core comprising a mixture of a progestogenic steroidal compound and an estrogenic steroidal compound in a ratio by weight of 10 parts of the progestogenic compound to 1.5-5 parts of the estrogenic compound, said progestogenic compound being initially dissolved in said polymer core in a degree of supersaturation of 1 to about 6 times of the amount by weight necessary for obtaining saturation concentration of said progestogenic compound in said polymer core material at 25.degree. C., and said polymer skin being permeable for both the progestogenic and the estrogenic compounds. 6. A drug delivery system according to claim 5, wherein the thermoplastic polymer used for the core material is an ethylene-vinylacetate copolymer, the thermoplastic polymer used for the skin material is an ethylene-vinylacetate copolymer, the thermoplastic polymer used for the skin material is an ethylene-vinylacetate copolymer, said core comprising a mixture of a progestogenic compound etonogestrel and an estrogenic compound ethinylestradiol in a ratio of 10 parts to 2-4 parts, said core comprising from 0.3 up to about 1% by weight of etonogestrel and from about 0.05 to about 0.3% by weight of ethinyl estradiol. 7. A drug delivery system according to claim 6, wherein the ratio of etonogestrel to ethinylestradiol is 10 parts to 2-3 parts, the weight percentage of etonogestrel being 0.5% and 1.0%. 8. A drug delivery system according to claim 6, characterised in that the skin is an ethylene-vinylacetate copolymer skin having a thickness ranging from 40 to 300 .mu.m and a vinylacetate content ranging from 5 to 15%. 9. A drug delivery system according to claim 8, characterised in that the skin thickness is 80 to 150 .mu.m and the vinyl acetate content is 9-10%. 10. A drug delivery system according to claim 5, wherein the core material is comprised of an ethylene-vinylacetate copolymer with a 25 to 35% vinyl acetate content. 11. A drug delivery system according to claim 5, wherein the core material comprises 0.55 to 0.8% by weight of etonogestrel and 0.12 to 0.18% by weight of ethinyl estradiol.