Osmotic dosage form composed of an extruded polymer tube form

Details Osmotic dosage form composed of an extruded polymer tube form Osmotic dosage form composed of an extruded polymer tube form

2002-10-24

2004-04-13

Tanner, Harry B. (Department: 3744)

Surgery

Controlled release therapeutic device or system

Osmotic or diffusion pumped device or system

C424S473000

Reexamination Certificate

active

06719751

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to dosage forms containing an extruded polymer tube. More specifically, the invention relates to polymer tube forms prepared by extrusion for the manufacture of osmotic dosage forms for administration of a therapeutic agent.
BACKGROUND OF THE INVENTION
One focus of efforts to improve drug therapy has been directed to providing drug dosage forms that provide controlled release of drug to the environment of use. Examples of such delivery systems include delayed-release and sustained-release systems. A particular approach to providing sustained release dosage forms that has found commercial success involves osmotic delivery systems, as described, for example, in U.S. Pat. Nos. 3,845,770 and 3,916,899. Osmotic dosage forms, in general, utilize osmotic pressure to generate a driving force for imbibing fluid into an internal compartment formed, at least in part, by a semipermeable wall that permits free diffusion of fluid but not drug or osmotic agent(s), if present. Following administration of the dosage form to a suitable fluid environment, such as the gastrointestinal tract or other body cavity or body tissue, fluid imbibition results in a deliverable drug-containing formulation being released from within the compartment through a suitable exit means formed through the semipermeable membrane. The rate of drug release is determined by the osmotic driving force.
Osmotic systems may be manufactured by forming the active agent and other ingredients for the internal compartment, such as an osmagent and osmopolymer, into a solid or semisolid by ballmilling, calendaring, stirring or rodmilling and then pressing into a preselected shape. The semipermeable wall material is dissolved in an appropriate solvent such as acetone or methylene chloride and is then applied to the pressed shape by molding, air spraying, dipping or brushing a solvent-based solution of the wall material onto the shape (U.S. Pat. Nos. 4,892,778, 4,285,987). Other methods for applying the semipermeable wall include an air suspension procedure, where the pressed shape is suspended and tumbled in a current of air and wall forming material (U.S. Pat. No. 2,799,241), and a pan coating technique. After application of the semipermeable wall to the pressed shape, a drying step is required and, then, suitable exit means for the active agent must be formed through the semipermeable membrane. Depending on the properties of the active agent and other ingredients within the internal compartment and the desired release rate for the dosage form, one or more orifices for active agent delivery are formed through the semipermeable membrane by mechanical drilling, laser drilling, or the like. The orifice may range in size from a single large orifice containing substantially an entire surface of the dosage form to one or more small orifices selectively located on the surface of the semipermeable membrane.
Dosage forms prepared by solvent-coating the semipermeable wall onto the pressed shape have been commercially successful, providing controlled and continuous release of various active agents to a variety of environments. There is, however, a need to improve the manufacture of the dosage forms. As mentioned above, the semipermeable wall is typically manufactured using an organic solvent such as acetone or methylene chloride. Manufacture of the wall via an organic solvent deposition process yields excellent membranes however there are disadvantages associated with the use of solvents. The solvents can be expensive, they are explosive, traces can be toxic and their use has a negative environmental impact. Further, after deposition of the semipermeable wall, the solvent must be removed by drying, requiring a further time-consuming processing step. After solvent removal, suitable exit means for the active agent must be provided by a drilling step requiring additional equipment and labor.
One approach to the manufacture of the above-described devices utilizing an injection molding process for manufacturing the semipermeable wall is described in U.S. Pat. No. 5,830,502. This process provides a dosage form prepared without the use of organic solvents. However, the injection molding process involves the use of specifically designed molds that can be expensive, as are the molding machinery and auxiliary equipment.
There is a remaining need to provide another approach for the manufacture of dosage forms having such a semipermeable wall. Ideally, this approach would reduce or eliminate some of the processing steps required by methods described above, such as solvent deposition of the semipermeable wall, solvent removal and drilling of suitable active agent exit means.
SUMMARY OF THE INVENTION
In one aspect, the present invention provides osmotic dosage forms and methods for manufacturing osmotic dosage forms having membranes that are essentially free of organic solvents. In this manner, problems associated with the storage, handling and use of such solvents are eliminated. In addition, the number of processing steps is reduced and processing time is decreased because the need for solvent drying is eliminated.
In another aspect, the present invention provides methods for manufacturing osmotic dosage forms having membranes that do not require a drilling step to form exit means for the therapeutic agent.
The invention is directed to osmotic dosage forms for delivery of a therapeutic agent comprising an internal compartment formed, at least in part, by a semipermeable wall that permits free diffusion of fluid but not therapeutic agent(s) or osmotic agent(s) wherein the semipermeable membrane comprises an extruded polymer tube. Disposed within the internal compartment is (i) a therapeutic agent and (ii) an expandable composition capable of absorbing biological fluid from an environment of use to thereby expand within the internal compartment and facilitate delivery of the therapeutic agent out of the internal compartment. The polymer tube circumscribes the internal compartment and is open at each end. Depending on the properties of the active agent and other ingredients within the internal compartment and the desired release rate for the dosage form, release of therapeutic agent may occur through either an open tube end (or ends) or through a suitably sized orifice, smaller than the open tube end, configured at the tube end(s). Such an orifice is formed, for example, by crimping or heat-sealing or the like, of the tube end to close the end except for a suitably sized orifice.
In certain embodiments, release of therapeutic agent occurs at both tube ends while, in other embodiments, release occurs at only one tube end. In these other embodiments, the tube end opposite to the tube end where therapeutic agent is released is preferably configured to be partially or completely closed to ensure that the adjacent component of the internal compartment remains in place within the internal compartment. Accordingly, the size of the polymer tube with respect to the size of the internal compartment is adapted to accommodate the need, when present, to close either or both of the tube ends.
In certain embodiments, the dosage form includes a first layer containing therapeutic agent adjacent one end of the polymer tube and a second layer containing the expandable composition adjacent the other tube end. If desired, additional layers containing therapeutic agent(s) may also be included in the internal compartment between the therapeutic agent layer adjacent one tube end and the expandable composition adjacent the opposite tube end. In these embodiments, therapeutic agent will be released from the tube end adjacent to the therapeutic agent layer(s) following administration of the dosage form. Accordingly, depending on the properties of the active agent and other ingredients within the internal compartment and the desired release rate for the dosage form, this tube end may be left open or may be closed to an extent that provides a suitably sized orifice for the delivery of the therapeutic agent(s) therethrough. The oppo

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