Osmotic system with laminated wall comprising structurally different semipermeable lamina

Claim 1

An oral osmotic system sized and adapted for the controlled administration of drug to an animal, said system comprising: a. a shaped laminated wall comprising (1) a lamina formed of a material that maintains its physical and chemical integrity in the presence of fluid, drug and during the dispensing of drug, and is permeable to the passage of fluid and impermeable to the passage of drug, said lamina formed of a material having the general formula: ##STR4## wherein R 5 is a member selected from the group consisting of hydroxyl, alkoxy, alkylcarbonate, alkylcarbamate, alkylsulfonate, alkylsulfamate and acyloxy, and wherein n is a positive number greater than 5 and at least one R is acyloxy, said lamina laminated to (2) a lamina formed of a different material that maintains its physical and chemical integrity in the presence of fluid, drug and during the dispensing of drug, and is permeable to the passage of fluid and impermeable to the passage of drug, said lamina formed of the different material selected from the general formula: ##STR5## wherein R 5 is a member selected from the group consisting of hydroxyl, alkoxy, alkylcarbonate, alkylcarbamate, alkylsulfonate, alkylsulfamate, and acyloxy, and wherein n is a positive number greater than 5 and at least one R is acyloxy; the wall surrounding and forming, b. a compartment containing a member selected from the group consisting of locally and systemically acting drugs; c. a passageway in the wall communicating with the compartment and the exterior of the system for administering drug from the system; and, d. wherein in operation when the system is in the animal fluid therefrom is imbibed through the laminated wall into the compartment in a tendency towards osmotic equilibrium at a rate determined by the permeability of the laminated wall and the osmotic pressure gradient across the laminated wall thereby continuously dissolving drug that is administered according to the following equation: h.sub.T /kπ.sub.T = h.sub.1 /kπ.sub.1 + h.sub.2 /kπ.sub.2 wherein h T is the thickness of the laminated wall, h 1 is the thickness of lamina (1,) h 2 is the thickness of lamina 2, kπ T is the osmotic pressure of drug in the compartment times the permeability of the laminated wall to fluid, kπ 1 is the osmotic pressure of drug in the compartment times the permeability of lamina (1) to fluid and kπ 2 is the osmotic pressure of drug in the compartment times the permeability of lamina (2) to fluid, through the passageway at a controlled and continuous rate over a prolonged period of time.