Medical injector with dose knob activation for automated reconstitution

A medical injector is provided herein having a body and a reservoir disposed in the body, the reservoir including at least first and second mixable components. At least one stopper is associated with the reservoir where distal advancement of the stopper over a predetermined distance causes mixing of the mixable components. A plunger is disposed in the body, along with a knob stem and a knob fixed to the knob stem so as to be rotatable therewith. A sleeve is telescopingly disposed over the knob stem, wherein the knob stem and the sleeve have cooperating elements formed thereon which selectively permit rotation of the knob stem to be transmitted to the sleeve so that the knob stem and the sleeve may rotate together. A spring is also provided for urging the sleeve distally. A releasable retainer releasably retains the sleeve against force of the spring. Rotation of the knob releases the sleeve and allows the spring to displace the sleeve distally. Distal movement of the sleeve causes distal movement of the plunger which causes distal movement of the stopper thus causing mixing of the mixable components. Advantageously, with the subject invention, a medical injector may be provided where autoreconstitution can be achieved by the turning of a knob.

FIELD OF THE INVENTION

This invention relates to autoreconstitution devices and, more particularly, to autoreconstitution devices having dose-setting mechanisms.

BACKGROUND OF THE INVENTION

Certain drugs or medicaments (those terms being used interchangeably herein) are preferably provided in powder or dry form (such as a lyophilized form), and require reconstitution prior to administration. Lyophilized drugs, for example, typically are supplied in a freeze-dried form that needs to be mixed with a diluent to reconstitute the substance into a form that is suitable for injection. Medicaments may also be provided in other dry or powder form that require reconstitution.

In addition, drugs may be provided as multipart systems which require mixing prior to administration. For example, one or more liquid (e.g., flowable (slurry or liquid)) components, and/or dry (e.g., powdered or granular) components may be provided in a drug container or delivery device which require mixing prior to administration. The components can be mixed and used to form various administratable drugs, such as insulin.

Prior art devices have been developed that provide a wet component (e.g., liquid) and a dry component (e.g., powder) in separate chambers of a common container with the container being configured to permit the flow of the wet component to the dry component to cause mixing thereof in preparing an administratable solution for injection. U.S. Pat. No. 4,874,381 to Vetter is directed to an injector having a barrel configured for mixing, while U.S. Pat. No. 4,968,299 to Ahlstrand et al. is directed to a drug cartridge having a barrel configured for mixing. Both Vetter et al. and Ahlstrand et al. disclose typical configurations for mixing where a bypass channel is formed in the barrel of the device. As such, the device must be specifically configured for mixing.

Manual force may be applied to a reconstitution device to cause the mixing of the multiple components. In addition, autoreconstitution devices have been developed in the prior art which provide a trigger-activated automated reconstitution. U.S. Pat. No. 6,793,646 to Giambattista et al. is an example of an autoreconstitution device. U.S. Pat. No. 6,793,646 is incorporated by reference in its entirety herein. The Giambattista et al. injector includes telescoping upper and lower body portions. Autoreconstitution is achieved by telescopingly collapsing the body parts together, thus releasing a spring that forces the reconstitution. It has been found that the Giambattista et al. type device requires a fairly substantial amount of force to activate and is difficult for some. In addition, components occasionally get stuck, thus rendering the injector inoperable.

SUMMARY OF THE INVENTION

A medical injector is provided herein having a body with a proximal end and a distal end. A reservoir is disposed in the body, the reservoir including at least first and second mixable components. At least one stopper is associated with the reservoir where distal advancement of the stopper over a predetermined distance causes mixing of the mixable components. A plunger is disposed in the body, along with a knob stem and a knob fixed to the knob stem so as to be rotatable therewith. A sleeve is telescopingly disposed over the knob stem, wherein the knob stem and the sleeve have cooperating elements formed thereon which selectively permit rotation of the knob stem to be transmitted to the sleeve so that the knob stem and the sleeve may rotate together. A spring is also provided for urging the sleeve distally. A releasable retainer releasably retains the sleeve in a first position against force of the spring. The releasable retainer includes a detent formed on one of the body and the sleeve, and, a channel formed in the other of the body and sleeve. The channel has a first part disposed partially circumferentially about a longitudinal axis of the sleeve, and a second part extending from the first part and disposed generally parallel to the longitudinal axis. The channel is formed to receive the detent and to permit sliding movement of the detent therealong. The sleeve is retained in the first position with the tab being located in the first part of the channel. Rotation of the knob causes the detent to move into the second part of the channel thus allowing the spring to displace the sleeve distally. Distal movement of the sleeve causes distal movement of the plunger which causes distal movement of the stopper thus causing mixing of the mixable components. Advantageously, with the subject invention, a medical injector may be provided where autoreconstitution can be achieved by the turning of a knob.

These and other features of the invention will be better understood through a study of the following detailed description and accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the figures, a medical injector10is shown having a body12with a distal end14and a proximal end16. The distal end14is intended to be directed towards a patient during use while the proximal end16is intended to be directed away from a patient during use. The medical injector10includes features18to which a needle assembly may be mounted in any known manner, such as threads.

A reservoir20is disposed in the body12for accommodating first and second mixable components22,24. At least one stopper26is associated with the reservoir20configured such that distal advancement of the stopper26over a predetermined distance shall cause mixing of the first and second mixable components22,24. Any known arrangement for allowing such mixing may be utilized. By way of non-limiting example, the first and second mixable components22,24may be separated by a secondary stopper28. The secondary stopper28divides the reservoir20into first and second chambers30,32, respectively, accommodating the first and second mixable components22,24. A septum34seals off the distal end of the first chamber30, while the stopper26is positioned to seal off the proximal end of the second chamber32. Preferably, if a dry component is used as one of the mixable components, the dry mixable component is located in the first chamber30.

One or more by-pass channels36are formed in the wall of the reservoir20. In an initial state, as shown inFIG. 2, the secondary stopper28is located at least partially proximally of the by-pass channels36so as to define a seal between the first and second chambers30,32and to define a seal between the second chamber32and the by-pass channels36. With distal advancement of the stopper26, and with the second mixable component24being wet and generally incompressible, force of movement of the stopper26is transmitted to the secondary stopper28through the second mixable component24. With sufficient distal movement of the secondary stopper28, the second chamber32comes into communication with the by-pass channels36, thus allowing the second mixable component24to be urged into the first chamber30with further distal movement of the stopper26. With reference toFIG. 5, with sufficient distal advancement of the stopper26, the second chamber32is collapsed with none or substantially none of the second mixable component24remaining therein. In addition, the secondary stopper28is located so as to define a seal between the first chamber30and the by-pass channels36. The first and second mixable components22,24are mixed within the first chamber32, such as through agitation of the medical injector10, so as to produce an injectable solution29, ready for injection.

The reservoir20is defined in a barrel38. The barrel38may be the barrel of a separate drug cartridge (FIG. 2) or a portion of the medical injector10.

As will be recognized by those skilled in the art, other arrangements for permitting reconstitution may be utilized. In addition, more than two-part systems, such as three-part and so forth, systems may be utilized. Active medical ingredients may be included in one or both of the first and second mixable components22,24. The first mixable component22may be dry (e.g., a powder or granular substance) and/or a liquid (e.g., flowable (slurry or liquid)). As mentioned above, the second mixable component24is preferably only a wet flowable component such as a liquid or slurry.

A tubular plunger40is positioned and configured to engage the stopper26. A knob stem42is provided which, preferably, extends into at least a portion of the plunger40. A sleeve44is telescopingly disposed over the knob stem42and configured to engage the plunger40. A knob46is fixed to the knob stem42so as to be rotatable therewith. The knob46is located exteriorly of the body12and proximate to the proximal end16.

The knob stem42and the sleeve44have cooperating elements formed thereon which selectively permit rotation of the knob stem42to be transmitted to the sleeve44so that the knob stem42and the sleeve44may rotate together. In a preferred arrangement, a protrusion48extends from the knob stem42which is received in a slot50formed in the sleeve44. The interengagement of the protrusion48and the slot50causes the sleeve44to rotate with the knob stem42. As shown inFIG. 5, and discussed below, with distal displacement of the sleeve44, the protrusion48is configured to be removed from the slot50so as to permit rotation of the knob stem42separate from the sleeve44. As will be appreciated by those skilled in the art, the protrusion48may be formed on the sleeve44and the slot50may be formed on the knob stem42as an alternative.

A spring52is provided to distally urge the sleeve44. It is preferred that the spring52be located about the sleeve44to act between sleeve shoulder54and rear face56. The spring52may be a coil or compression spring. Alternatively, as recognized by those skilled in the art, various biasing elements may be utilized as the spring.

FIG. 2shows the sleeve44being retained in a first position against force of movement generated by the spring52. A releaseable retainer58is provided which retains the spring52in the first state. With reference toFIGS. 3 and 4, the releaseable retainer58includes a detent60located on the sleeve44, preferably adjacent to the sleeve shoulder54, and a channel62formed in the body12. The channel62includes a first part64which partially extends about a longitudinal axis66of the sleeve44. The channel62also includes a second part68which extends from the first part64and is generally parallel to the longitudinal axis66. The channel62may have a general L-shape. The channel62is formed to receive the detent60and to permit sliding movement of the detent60therealong. The arrangement of the detent60and the channel62may be reversed with the detent60located on the body12and the channel62located on the sleeve44.

With reference toFIGS. 3 and 4, the detent60is shown to be nested in the first part64of the channel62. In this state, the sleeve44is retained in the first position. With rotation of the knob46, the knob stem42is caused to rotate, and, in turn, the sleeve44is caused to rotate. Such rotation causes the detent60to move into the second part68of the channel62thus allowing the spring52to distally advance the sleeve44. As shown inFIG. 5, the sleeve44is advanced distally causing the plunger42to advance distally, and, in turn, causing the stopper26to advance distally thus causing mixing of the first and second mixable components22,24. Distal movement of the sleeve44under force of the spring52may be limited due to interengagement of the sleeve shoulder54with a stop surface70formed on the body12and/or engagement with the barrel38.

It is preferred that the mixing of the components be conducted without a needle mounted to the medical injector10. As such, the reservoir20is not vented during the mixing. With a needle being mounted to the medical injector10after the mixing, any residual gases trapped in the reservoir20are purged through the needle. It may be preferred to not provide a physical stop to the distal advancement of the plunger40. In this manner, the mixed components may be maximally compressed under force of the spring52. With mounting of a needle onto the medical injector10, the reservoir20is vented thus permitting further distal advancement of the plunger40. This secondary distal advancement may assist in priming a needle for use.

Once mixed, the size of a dose to be administered by the medical injector10may be adjusted. With reference toFIG. 6, the knob stem42is provided with a plurality of axially and radially spaced-apart abutment surfaces72. The abutment surfaces72correspond to different administrable dosage amounts. An engagement surface74is defined on the plunger40. Rotation of the knob stem42causes radial displacement of the abutment surfaces72. The abutment surfaces72are axially alignable with the engagement surface74such that with sufficient distal displacement of the knob stem42at least one of the abutment surfaces72will be caused to engage the engagement surface74and transmit force of movement to the plunger40. In this manner, distal displacement of the knob stem42may be transmitted to the plunger40. Moreover, stroke length corresponding to the movement of the plunger40may be adjusted depending on the abutment surface72which is in engagement with the engagement surface74. The greater the initial distance of the abutment surfaces72from the engagement surface74, the corresponding smaller dose that will be caused to be administered. Regardless of the selected dose amount, it is preferred that the knob stem42having a fixed length of stroke for distal displacement during administration of an injection. The further abutment surfaces72have greater lost motion with distal movement of the knob stem42and, thus, less distance engaging the engagement surface74. The extent of movement of the plunger40dictates the extent of movement of the stopper26and, thus, dictates the amount of the injectable solution29to be driven from the reservoir20in an injected dose.

The dose is selected by rotating the dose knob46. Indicia may be provided on the body12and/or the dose knob46in facilitating dose setting. To prevent the dose knob from being inadvertently turned prior to mixing of the mixable components22,24, the knob stem42may be coupled to the sleeve44so as to prevent relative rotation therebetween, as described above. With reconstitution, the sleeve44may decouple from the knob stem42so as to permit relative rotation therebetween. In addition, with reference toFIG. 6, a groove76may be formed in the knob stem42corresponding to a rib78formed on the plunger40. In an initial state, as shown inFIG. 2, the rib78nests within the groove76so as to prevent relative rotation between the plunger40and the knob stem42. With reconstitution being completed, the plunger40may be advanced so as to have the rib78removed from the groove76. The knob stem42is then free to rotate in setting a dose. Alternatively, the rib78may still be partially nested in the groove76even in a post-reconstituted state. With this configuration, the knob stem42is proximally displaced to have the rib78removed from the groove76thus permitting subsequent dose setting. The dose is administered by causing distal advancement of the knob46once the dose has been properly set.

It is noted that the engagement surface74may be located at a proximal end80of the rib76.

It is preferred that the knob46be releasably retained in positions corresponding to the various dose settings. In this manner, it is preferred that once a dose has been set, there is no rotation of the knob46during distal displacement thereof, thus avoiding that an improper of the abutment surfaces72engage the engagement surface74. Such an arrangement is disclosed in U.S. Pat. No. 6,793,646. As shown in U.S. Pat. No. 6,793,646, with reference toFIG. 7, one or more tabs82may be formed on the knob46which are selectively engageable with positioning channels84formed on a portion of the body12. Positioning channels84are circumferentially separated by dividers86and positioned to correspond to the abutment surfaces72. The tabs82nest in the positioning channels84at given radial positions of the knob46corresponding to different dose sizes. With turning of the knob46, the tabs82are caused to by-pass the dividers86and move into a corresponding of the positioning channels84. The positioning channels84maintain the radial position of the knob46.

In addition, it is preferred that the knob46be maintained in an axial position so as to permit a fixed stroke length of distal advancement for dose administration. One or more retaining ribs88may be located along the positioning channels84so as to limit axial movement of the tabs82. With a dose having been selected, the knob46may be distally advanced with the tabs82by-passing the retaining ribs88. It is preferred that the tabs82and the retaining ribs88be configured so as to provide a locking affect so as to prevent rearward retraction of the knob46and re-use of the medical injector10.

As will be understood by those skilled in the art, the body12may be formed of one or more components with the features described herein being formed on any of those one or more components.