Structured bioerodible drug delivery device

Claim 1

A delivery device for the sustained administration of a predetermined dosage of an ophthalmic drug to the eye of a mammalian patient comprising (1) an inner reservoir comprised of a biodegradable material that degrades to innocuous products in response to the biological ocular environment of the patient, said reservoir containing an ophthalmic drug formulation confined therein, and (2) an outer membrane surrounding the inner reservoir, the membrane permeable to the passage of ophthalmic drug, but at a lower rate than through the inner reservoir, the membrane formed from drug release rate controlling bioerodible material consisting of a polyvalent metal ion cross-linked anionic polyelectrolyte, said ion a member selected from the group consisting of aluminum, barium, cadmium, calcium, copper, iron, zinc and mixtures thereof, said polyelectrolyte a member selected from the group consisting of cellulose, hemicellulose, starch, polystyrene sulfonic acid, polyvinyl sulfonic acid, polyvinyl methylol sulfonic acid, polyacrylic acid, polymethacrylic acid, acrylic copolymers, methacrylic copolymers, polyvinyl alcohol, polyvinyl chloride, glycans and polysaccharides, which outer membrane bioerodes in the eye of the patient in response to the biological environment therein by a process of polyvalent metal ion displacement by noncross-linking ions present in the eye, and wherein when in the ocular environment the membrane continuously meters the flow of a therapeutically effective amount of ophthalmic drug from the reservoir to the eye of the patient at a controlled and continuous rate over a prolonged period of time.