Sustained release

Claim 2

An injectable dispensing system for releasing a substance at a substantially constant rate in an environment immediately adjacent said dispensing system that depletes said substance, said system comprising: a microcapsule having a membrane comprising a matrix of polycationic polymer salt bonded to a polyanionic polymer which defines an intracapsular volume, said membrane having a multiplicity of pores of dimensions sufficient to limit the rate at which the molecules of said substance pass therethrough from said intracapsular volume; and disposed within said volume, for purposes of maintaining a given extracapsular concentration in said environment, a concentration of aid substance at least two orders of magnitude greater than said given extracapsular concentration which results in an osmotic pressure sufficient to sustain said limited rate when said capsule is placed in said environment.

Claim 3

The system of claim 1 wherein said substance is a solid disposed within said intracapsular volume in a solvent for said solid.

Claim 4

The system of claim 2 wherein said solid is sparingly soluble in said solvent.

Claim 5

The system of claim 1 wherein said substance comprises a biologically active material.

Claim 6

The system of claim 4 wherein said biologically active material is selected from the group consisting of hormones, enzymes, antibodies, vaccines, drugs, and lymphokines.

Claim 7

The system of claim 1 further comprising, for storage purposes, means defining an extracapsular volume of said substance adjacent the exterior of said capsule, said extracapsular volume containing a concentration of said substance sufficient to substantially prohibit a net flow of said substance from said intracapsular volume to said extracapsular volume.

Claim 8

The system of claim 1 wherein said membrane defines a sphere having a diameter between about 0.1 and 3.0 mm.

Claim 9

A process for administering a substance to an animal at a substantially constant rate for purposes of maintaining a given extracapsular concentration of said substance adjacent the exterior of said capsule within said animal, said process comprising the steps of: A. providing a dispensing system comprising: a microcapsule having a membrane comprising a matrix of polycationic polymer salt bonded to a polyanionic polymer which is physiologically compatible with said animal and which defines an intracapsular volume, said membrane having a multiplicity of pores of dimensions sufficient to limit the rate at which the molecules of said substance pass therethrough from said intracapsular volume; and disposed with said volume, a concentration of said substance at least two orders of magnitude greater than said given extracapsular concentration which results in an osmotic pressure sufficient to sustain said limited rate when said capsule is placed in said animal; and B. Injecting said dispensing system within the body of said animal.

Claim 10

A process for administering a substance to an animal at a substantially constant rate for purposes of maintaining a given extracapsular concentration of said substance adjacent the exterior of said capsule within said animal, said process comprising the steps of: A. providing a dispensing system comprising: a microcapsule having a membrane comprising a matrix of polycationic polymer salt bonded to a polyanionic polymer which is physiologically compatible with said animal and which defines an intracapsular volume, said membrane having a multiplicity of pores of dimensions sufficient to limit the rate at which the molecules of said substance pass therethrough from said intracapsular volume; and disposed with said volume, a concentration of said substance at least two orders of magnitude greater than said given extracapsular concentration which results in an osmotic pressure sufficient to sustain said limited rate when said capsule is placed in said animal; and B. Injecting said dispensing system within the body of said animal.

Claim 11

The process of claim 8 wherein said dispensing system comprises a plurality of said capsules.

Claim 12

The process of claim 8 wherein said substance is a solid disposed within said intracapsular volume in a solvent for said solid.

Claim 13

The process of claim 10 wherein said solid is sparingly soluble in said solvent.

Claim 14

The process of claim 8 wherein said substance comprises a biologically active material.

Claim 15

The process of claim 12 wherein said biologically active material is selected from the group consisting of hormones, enzymes, antibodies, vaccines, drugs, and lymphokines.

Claim 16

A dispensing system for releasing a substance at a substantially constant rate in an environment immediately adjacent said dispensing system that depletes said substance, said substance comprising: a microcapsule having a membrane comprising a matrix of polycationic polymer salt bonded to a polyanionic polymer which defines an intracapsular volume, said membrane having a mulitplicity of pores of dimensions sufficient to limit the rate at which the molecules of said substance pass therethrough from said intracapsular volume; and disposed within said volume, for purposes of maintaining a given extracapsular concentration in said environment, a concentration of said substance at least two orders of magnitude greater than said given extracapsular concentration which results in an osmotic pressure sufficient to sustain said limited rate when said capsule is placed in said environment.

Claim 17

A dispensing system for releasing a substance at a substantially constant rate in an environment immediately adjacent said dispensing system that depletes said substance, said substance comprising: a microcapsule having a membrane comprising a matrix of polycationic polymer salt bonded to a polyanionic polymer which defines an intracapsular volume, said membrane having a mulitplicity of pores of dimensions sufficient to limit the rate at which the molecules of said substance pass therethrough from said intracapsular volume; and disposed within said volume, for purposes of maintaining a given extracapsular concentration in said environment, a concentration of said substance at least two orders of magnitude greater than said given extracapsular concentration which results in an osmotic pressure sufficient to sustain said limited rate when said capsule is placed in said environment.

Claim 18

The system of claim 14 wherein said substance is selected from the group consisting of plant fertilizers, pesticides, fungicides, and plant hormones.

Claim 19

The system of claim 14 wherein said substance is selected from the group consisting of flavors, perfumes, and preservatives.

Claim 20

The system of claim 14 wherein said substance is a tissue culture nutrient.