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Claims for Patent: 4,957,119

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Claims for Patent: 4,957,119

Title: Contraceptive implant
Abstract:The invention relates to an implant of polymeric material which can release a contraceptive agent for a relatively long time when fitted subcutaneously or locally. The implant comprises a core material of ethylene/vinyl acetate copolymer which functions as a matrix for a contraceptive substance, an ethylene/vinyl acetate membrane encasing the core material, and a contact layer at the interface of the core material and membrane which prevents the separation of the core material from the membrane. The implant of the invention is made by a co-extrusion process.
Inventor(s): de Nijs; Hendrik (Oss, NL)
Assignee: Akzo N.V. (Arnhem, NL)
Application Number:07/229,066
Patent Claims: 1. An implant intended for subcutaneous or local administration, comprising:

core material of ethylene/vinyl acetate copolymer having such a molecular weight that the melt index is greater than 10 grams/10 minutes, and a vinyl acetate content of at least 20% by weight, which core material functions as a matrix for at least one contraceptive substance selected from the group consisting of 3-keto-desogestrel, levonorgestrel and gestodene in a quantity which is sufficient for a constant release of at least 15-30 .mu.g contraceptive substance per day over a predetermined term, and

a membrane having a layer thickness of 50-250 .mu.m which encases the core material and also consists of ethylene/vinyl acetate copolymer, but with such a molecular weight that the melt index is less than 10 grams/10 minutes and a vinyl acetate content of less than 20% by weight, which membrane, with the core material, forms a contact layer at the interface of the core material and membrane, said contact layer preventing the core material and membrane from separating from one another.

2. The implant of claim 1, wherein the core material comprises an ethylene/vinyl acetate copolymer with a melt index between 25 and 30 grams/10 minutes and a vinyl acetate content of greater than 25% by weight.

3. The implant of claim 1 wherein the membrane comprises ethylene/vinyl acetate copolymer with a melt index of 8 grams/10 minutes or less, and a vinyl acetate content of less than 20% by weight.

4. Implant according to claim 1, wherein the contraceptive substance comprises 3-keto-desogestrel.

5. Implant according to claim 1, which is of essentially cylindrical shape with a maximum external diameter of about 2 mm and a length of less than about 5 cm.

6. The implant of claim 1 wherein said core consists of from 50 to 75% contraceptive substance and from 50 to 25% ethylene/vinyl acetate copolymer.

7. The implant of claim 6 wherein the ends of the implant are covered by an inert polymer.

8. The implant of claim 7 further comprising a layer of polysiloxane coating the entire implant.

9. An implant comprising:

a core including a contraceptive substance selected from the group consisting of 3-keto-desogestrel, levonorgestrel, gestodene, and mixtures thereof, in a matrix consisting of ethylene/vinyl acetate copolymer having a melt index greater than 10 grams/10 minutes, and further having a vinyl acetate content of at least 20% by weight, the contraceptive substance present in the matrix in a sufficient amount to release at least 15-30 .mu.g of contraceptive substance per day from the implant over a predetermined term;

a membrane for controlling the rate of contraceptive substance release from the implant, said membrane having a layer thickness of 50-250 .mu.m encasing said core, said membrane consisting of ethylene/vinyl acetate copolymer having a molecular weight such that the membrane's melt index is less than 10 grams/10 minutes and further having a vinyl acetate content of less than 20% by weight; and

a contact layer, at the interface of said core and said membrane, said contact layer preventing the separation of said membrane from said matrix.

10. The implant of claim 9 wherein said core consists of from 50 to 75% contraceptive substance and from 50 to 25% ethylene/vinyl acetate copolymer by weight.

11. The implant of claim 10 wherein the ends of the implant are covered by an inert polymer.

12. The implant of claim 10 further comprising a layer of polysiloxane coating the entire implant.

13. The implant of claim 11 further comprising a layer of polysiloxane coating the entire implant.

14. The implant of claim 13 wherein the ethylene/vinyl acetate copolymer of the core has a melt index between 25 and 30 grams/10 minutes and a vinyl acetate content of greater than 25% by weight.

15. The implant of claim 13 wherein the ethylene/vinyl acetate copolymer of the membrane has a melt index less than 8 grams/10 minutes and a vinyl acetate content of less than 20% by weight.
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