Rate-controlled drug release system

Claim 2

In a drug release device for the continuous and controlled administration of a drug over a prolonged period of time, said device comprising a reservoir containing the drug in a pharmaceutically acceptable carrier and a medically acceptable, outer polymeric membrane surrounding said reservoir, said polymeric membrane being formed of a drug release rate-controlling material which is permeable to the passage of said drug by diffusion, the improvement which comprises: (a) forming said membrane from a block copolymer of poly(ether-urethane) and poly(dimethyl siloxane) and (b) employing as the drug a lipophilic drug having a structural molecular weight below about 1000.

Claim 3

The improvement according to claim 1 wherein said block copolymer is pre-treated with a solvent mixture of ethylene glycol and a C 2-3 alcohol for a period of time effective to increase the permeability of said block copolymer.

Claim 4

The improvement according to claim 2 wherein the C 2-3 alcohol is ethyl alcohol.

Claim 5

The improvement according to claim 3 wherein the solvent mixture is a 1:1 volume mixture.

Claim 6

The improvement according to claim 2 wherein the C 2-3 alcohol is n-propyl alcohol.

Claim 7

The improvement according to claim 2 wherein the C 2-3 alcohol is isopropyl alcohol.

Claim 8

The improvement according to claim 1 wherein the reservoir contains a saturated solution of the lipophilic drug in a pharmaceutically acceptable solvent.

Claim 9

The improvement according to claim 7 wherein the solution is supersaturated.

Claim 10

The improvement according to claim 1 wherein the lipophilic drug is phenytoin.

Claim 11

The improvement according to claim 1 wherein the lipophilic drug is primidone.

Claim 12

The improvement according to claim 1 wherein the lipophilic drug is dapsone.

Claim 13

The improvement according to claim 1 wherein the device additionally comprises a second polymeric membrane interposed between the outer polymeric membrane and the drug reservoir, said second polymeric membrane comprising a medically acceptable, inert, microporous polymeric material having a plurality of micropores with a pore size of about 1 nm to about 100 μm, and a medically acceptable drug release rate controlling material which is permeable to the passage of said drug by diffusion housed in the micropores, the rate of diffusion of the drug through the second polymeric membrane per unit area of polymeric membrane cross-sectional flow path per unit of polymeric membrane thickness is less than the rate of diffusion of the drug through the outer polymeric membrane per unit area of polymeric membrane cross-sectional flow path per unit of polymeric membrane thickness.

Claim 14

The improvement according to claim 12 wherein the material in the micropores is a copolymer of poly(etherurethane) and poly(dimethyl siloxane).

Claim 15

The improvement according to claim 13 wherein the copolymer is formed in the micropores by a solvent coating process of a block copolymer of said copolymer followed by a cross-linking process to form the cross-linked copolymer.

Claim 16

The improvement according to claim 12 wherein the material in the micropores is a copolymer formed in the micropores by a glow discharge polymerization process.

Claim 17

The improvement according to claim 15 wherein the copolymer comprises hexamethyl disiloxane as one monomer and ethylene, allene or allylamine as a second monomer.