United States Patent:  5,997,902

Assignee:  Alza Corporation (Palo Alto, CA)

Filed:  August 3, 1998

The present invention is concerned with improving the delivery of a drug from a ruminal delivery device to give a consistent delivery of drug to the ruminal environment. Thus, the invention is directed to an improved ruminal drug delivery device comprising a semipermeable membrane having an exit orifice and defining a compartment, the compartment containing a swellable osmotic agent expandable driving member, a drug to be dispensed, a density element and, optionally, a partition layer between the osmotic expandable driving member and the drug formulation, wherein the improvement comprises an essentially gas-impermeable barrier means that separates the density element from the other components within the delivery device for isolating gases evolved from the density element from the other components within the delivery device. The barrier means further includes a coupling to transfer osmotic pressure to the semipermeable wall. The invention is also directed to methods and articles for providing a consistent delivery of drug from a ruminal drug delivery device.

SUMMARY OF THE INVENTION

The present invention is concerned with improving the delivery of a drug from a ruminal delivery device to give a consistent delivery of drug to the ruminal environment. Thus, the invention is directed to an improved ruminal drug delivery device comprising a semipermeable cup having an open end, a crimped portion adjacent the open end, and an exit orifice. The cup contains an osmotic expandable driving member, a drug to be dispensed, a density element and, optionally, a moveable partition layer between the osmotic expandable driving member and the drug formulation. An essentially gas-impermeable barrier means separates the density element from the other components within the delivery device to isolate gases evolved from the density element from the other components within the delivery device. According to the present invention, a coupling between the density element and the semipermeable cup reduces the stress applied to the crimped portion of the semipermeable cup. This provides additional means to retain the density element within the semipermeable cup.

This invention is also directed to an article which improves the performance of a ruminal drug delivery device. The article comprises an essentially gas-impermeable sleeve which is sized and shaped to be placed between the density element and the other components within the ruminal device. The sleeve surrounds and tightly engages the density element. The sleeve also acts as a barrier means to protect the drug formulation and other components from gas evolved during corrosion of the density element, thus providing a more constant and consistent delivery profile of drug from the device. Projections on the sleeve may engage with receiving depressions defined within the wall to act as a coupling to hold the density element within the compartment and alternatively, the sleeve may be directly bonded to the semipermeable wall.

Claim 1 of 7 Claims

1. An insert for use in combination with a ruminal drug delivery device having a semipermeable cup defining a compartment, an osmotic expandable driving member, a drug formulation containing a drug to be dispensed, a density element, and exit means for fluidly connecting the drug formulation with the environment of use, the insert being essentially gas-impermeable and being sized and shaped to be placed between a density element and the drug formulation.

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