Osmotic pump with self-retaining, fast-start membrane plug

Abstract

An osmotic pump includes a capsule having at least one delivery port formed at a first end and a membrane plug retained in a second end of the capsule remote from the delivery port to provide a fluid-permeable barrier between an interior and an exterior of the capsule. The membrane plug has a columnar body and at least one slot formed in the columnar body to vent pressure from the interior to the exterior of the capsule when the columnar body extends a predetermined distance relative to the second end of the capsule, thereby preventing expulsion of the membrane plug from the second end.

1 . An osmotic pump, comprising:
 a capsule having at least one delivery port formed at a first end; and   a membrane plug retained in a second end of the capsule remote from the delivery port to provide a fluid-permeable barrier between an interior and an exterior of the capsule;   wherein the membrane plug has a columnar body and at least one slot formed in the columnar body to vent pressure from the interior to the exterior of the capsule when the columnar body extends a predetermined distance relative to the second end of the capsule, thereby preventing expulsion of the membrane plug from the second end.   
   
   
       2 . The osmotic pump of  claim 1 , wherein the slot extends from a base of the columnar body and terminates at a non-basal point in the columnar body. 
   
   
       3 . The osmotic pump of  claim 2 , wherein the non-basal point is in a range from 10 to 90% of a length of the columnar body. 
   
   
       4 . The osmotic pump of  claim 2 , wherein the non-basal point is in a range from 20 to 80% of a length of the columnar body. 
   
   
       5 . The osmotic pump of  claim 2 , wherein the non-basal point is in a range from 30 to 60% of a length of the columnar body. 
   
   
       6 . The osmotic pump of  claim 1 , wherein the columnar body terminates in an enlarged end cap, the end cap having a surface for engagement with the second end of the capsule so as to establish a repeatable position of the columnar body in the capsule. 
   
   
       7 . The osmotic pump of  claim 1 , wherein a plurality of protrusions are provided on the surface of the columnar body for engaging an inner surface of the capsule. 
   
   
       8 . The osmotic pump of  claim 1 , wherein the membrane plug is made of a semipermeable material. 
   
   
       9 . The osmotic pump of  claim 1 , further comprising a first and a second chamber defined in the capsule for containing an osmotic agent and a beneficial agent, respectively. 
   
   
       10 . The osmotic pump of  claim 9 , further comprising a piston movably disposed between the first and second chambers. 
   
   
       11 . The osmotic pump of  claim 1 , wherein the delivery port is provided by a diffusion moderator retained in the first end of the capsule. 
   
   
       12 . The osmotic pump of  claim 1 , wherein an orifice is provided in the columnar body to allow fluid flow through the columnar body until the orifice becomes occluded due to swelling of the columnar body. 
   
   
       13 . The osmotic pump of  claim 12 , wherein a diameter of the orifice is less than 35% of a diameter of the columnar body. 
   
   
       14 . The osmotic pump of  claim 12 , wherein a diameter of the orifice is in a range from 0.8 to 33% of a diameter of the columnar body. 
   
   
       15 . A membrane plug for use with an osmotic pump having a delivery capsule, comprising:
 a columnar body made of a semipermeable material, the columnar body having an outer surface for engagement with an inner surface of the capsule and being provided with a slot, the slot extending from a base of the columnar body to a non-basal point on the outer surface of the columnar body so that pressure can be selectively vented from an interior to an exterior of the capsule.   
   
   
       16 . The membrane plug of  claim 15 , wherein the non-basal point is in a range from 10 to 90% of a length of the columnar body. 
   
   
       17 - 19 . (canceled) 
   
   
       20 . The membrane plug of  claim 15 , wherein a plurality of protrusions are provided on the surface of the columnar body for engagement with the inner surface of the capsule. 
   
   
       21 - 23 . (canceled) 
   
   
       24 . A membrane plug for use with an osmotic pump having a delivery capsule, comprising:
 a columnar body made of a semipermeable material, the columnar body having an outer surface for engagement with an inner surface of the capsule and being provided with an orifice that allows fluid flow into the capsule until the orifice becomes occluded due to swelling of the semipermeable material.   
   
   
       25 . The membrane plug of  claim 24 , wherein a diameter of the orifice is less than 35% of a diameter of the columnar body. 
   
   
       26 . The membrane plug of  claim 24 , wherein a diameter of the orifice is in a range from 0.8 to 33% of a diameter of the columnar body.