Plungers for drug delivery devices

Abstract

A plunger configured as described herein provides geometry optimizations to minimize friction magnitude and variability during use by maintaining low deformation under large extrusion forces. More specifically, plunger embodiments described herein minimize a contact area between the plunger and a syringe or chamber, while also maintaining high contract pressures to maintain container closure integrity. Moreover, the plunger embodiments are configured to have minimal or no increase in the contact area under high loads associated with the delivery of viscous products.

What is claimed is: 
     
         1 . A drug delivery assembly comprising:
 a plunger including:   a body portion having a sidewall, a leading surface, and a trailing surface, wherein the body portion does not include a cavity having an opening defined in the trailing surface configured to receive a plunger rod therein, and a ribbed portion comprising a plurality of ribs projecting radially outwardly from the sidewall of the body portion and spaced axially apart from one another, the plurality of ribs comprising at least a trailing rib and a leading rib, each of the ribs including an annular configuration;   a chamber with an annular sidewall extending between a first, open end and a second end having a dispensing opening, the plunger received within the chamber so that the ribs thereof seal against an interior surface of the sidewall; and   a drive member configured to drive the plunger through the chamber to the second end thereof,   the plunger having the plurality of ribs exhibiting a mean glide force in the range of approximately 0.4 to approximately 1.5 N, which represents a reduction in the mean glide force by at least 15% relative to a mean glide force of a plunger having a majority of the sidewall of the body portion contact the interior surface of the sidewall of the chamber.   
     
     
         2 . The drug delivery assembly of  claim 1 , wherein a standard deviation of the mean glide force of the plunger having ribs is in a range of approximately 0.02 to approximately 0.16, which represents a reduction in the standard deviation by at least 60% relative to a standard deviation from the mean glide force of the plunger having the majority of the sidewall of the body portion contact the interior surface of the sidewall of the chamber. 
     
     
         3 . The drug delivery assembly of  claim 1 , wherein radial surfaces of the body portion extending between the ribs include flat portions. 
     
     
         4 . The drug delivery device of  claim 1 , the plurality of ribs reducing the mean glide force by at least 70% relative to the mean glide force of the plunger having the majority of the sidewall of the body portion contact the interior surface of the sidewall of the chamber. 
     
     
         5 . The drug delivery assembly of  claim 4 , the plurality of ribs reducing a standard deviation from the mean glide force by at least 90% relative to a standard deviation from the mean glide force of the plunger having the majority of the sidewall of the body portion contact the interior surface of the sidewall of the chamber. 
     
     
         6 . The drug delivery device of  claim 4 , wherein radial surfaces of the sidewall extending between the ribs are concavely curved along a longitudinal axis of the body portion. 
     
     
         7 . The drug delivery assembly of  claim 1 , wherein the ribs are axially spaced apart from one another at least double a distance of plunger travel within the chamber during air transport. 
     
     
         8 . An autoinjector device comprising:
 a housing;   a syringe assembly at least partially received within the housing and including a syringe barrel with an annular sidewall extending between a first, open end and a second end having a dispensing opening;   an actuating mechanism at least partially received within the housing and including a plunger received within the syringe barrel, the plunger comprising:   a body portion having a sidewall, a leading surface, and a trailing surface, wherein the body portion does not include a cavity having an opening defined in the trailing surface configured to receive a plunger rod therein, and a ribbed portion comprising a plurality of ribs projecting radially outwardly from the sidewall of the body portion and spaced axially apart from one another, the plurality of ribs comprising at least a trailing rib and a leading rib, each of the ribs including an annular configuration and sized so that the ribs seal against an interior surface of the sidewall of the syringe barrel;   a drive mechanism; and   a drive member configured to be driven by the drive mechanism to push the plunger through the syringe barrel to the second end thereof to thereby force a medicament within the syringe barrel through the dispensing opening,   the plunger having the plurality of ribs exhibiting a mean glide force in the range of approximately 0.4 to approximately 1.5 N, which represents a reduction in the mean glide force by at least 15% relative to a mean glide force of a plunger having a majority of the sidewall of the body portion contact the interior surface of the sidewall of the syringe barrel.   
     
     
         9 . The drug delivery assembly of  claim 8 , wherein a standard deviation of the mean glide force of the plunger having ribs is in a range of approximately 0.02 to approximately 0.16, which represents a reduction in the standard deviation by at least 60% relative to a standard deviation from the mean glide force of the plunger having the majority of the sidewall of the body portion contact the interior surface of the sidewall of the syringe barrel. 
     
     
         10 . The drug delivery assembly of  claim 8 , wherein radial surfaces of the body portion extending between the ribs include flat portions. 
     
     
         11 . The drug delivery device of  claim 8 , the plurality of ribs reducing the mean glide force by at least 70% relative to the mean glide force of the plunger having the majority of the sidewall of the body portion contact the interior surface of the sidewall of the syringe barrel. 
     
     
         12 . The drug delivery assembly of  claim 11 , the plurality of ribs reducing a standard deviation from the mean glide force by at least 90% relative to a standard deviation from the mean glide force of the plunger having the majority of the sidewall of the body portion contact the interior surface of the sidewall of the syringe barrel. 
     
     
         13 . The drug delivery device of  claim 11 , wherein radial surfaces of the sidewall extending between the ribs are concavely curved along a longitudinal axis of the body portion. 
     
     
         14 . The drug delivery assembly of  claim 8 , wherein the ribs have at least 0.8 MPa contact pressure with the interior surface of the sidewall of the syringe barrel. 
     
     
         15 . An on-body injector device comprising:
 a housing having an interior and a bottom wall within an opening extending therethrough, the housing configured to be secured to the tissue of a user;   a reservoir with an annular sidewall extending between a first, open end and a second end having a dispensing opening;   a drive mechanism including a plunger received within the reservoir, the plunger comprising:   a body portion having a sidewall, a leading surface, and a trailing surface, wherein the body portion does not include a cavity having an opening defined in the trailing surface configured to receive a plunger rod therein, and a ribbed portion comprising a plurality of ribs projecting radially outwardly from the sidewall of the body portion and spaced axially apart from one another, the plurality of ribs comprising at least a trailing rib and a leading rib, each of the ribs including an annular configuration and being sized so that the ribs seal against an interior surface of the sidewall of the reservoir;   a drive member configured to drive the plunger through the reservoir to the second end thereof;   an insertion mechanism including a delivery member configured to shift from a retracted position within the housing to a deployed position extending outside of the housing through the opening thereof;   a fluid pathway assembly configured to fluidly couple the reservoir to the insertion mechanism; and   an actuator configured to cause the drive mechanism to drive the plunger through the reservoir to the second end thereof in response to an actuation thereof to thereby dispense medicament within the reservoir through the insertion mechanism,   the plunger having the plurality of ribs exhibiting a mean glide force in the range of approximately 0.4 to approximately 1.5 N, which represents a reduction in the mean glide force by at least 15% relative to a mean glide force of a plunger having a majority of the sidewall of the body portion contact the interior surface of the sidewall of the chamber.   
     
     
         16 . The drug delivery assembly of  claim 15 , wherein a standard deviation of the mean glide force of the plunger having ribs is in a range of approximately 0.02 to approximately 0.16, which represents a reduction in the standard deviation by at least 60% relative to a standard deviation from the mean glide force of the plunger having the majority of the sidewall of the body portion contact the interior surface of the sidewall of the syringe barrel. 
     
     
         17 . The drug delivery assembly of  claim 15 , wherein radial surfaces of the body portion extending between the ribs include flat portions. 
     
     
         18 . The drug delivery device of  claim 15 , the plurality of ribs reducing the mean glide force by at least 70% relative to the mean glide force of the plunger having the majority of the sidewall of the body portion contact the interior surface of the sidewall of the syringe barrel. 
     
     
         19 . The drug delivery assembly of  claim 18 , the plurality of ribs reducing a standard deviation from the mean glide force by at least 90% relative to a standard deviation from the mean glide force of the plunger having the majority of the sidewall of the body portion contact the interior surface of the sidewall of the syringe barrel. 
     
     
         20 . The drug delivery device of  claim 18 , wherein radial surfaces of the sidewall extending between the ribs are concavely curved along a longitudinal axis of the body portion.