Medication delivery pen

Details Medication delivery pen Medication delivery pen

1999-08-06

2001-08-21

Kennedy, Sharon (Department: 3763)

Surgery

Means for introducing or removing material from body for...

Treating material introduced into or removed from body...

C604S186000

Reexamination Certificate

active

06277099

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The subject invention relates to a diagnostic and medication delivery system having a medication delivery pen, blood monitoring device and a lancer removably mounted in a common housing.
2. Description of Related Art
Home diabetes therapy requires the patient to carry out a prescribed regimen that involves self-testing blood glucose levels and administering an appropriate dose of insulin. Insulin has traditionally been injected by a hypodermic syringe, which suffers from numerous drawbacks. For example, syringes are not preloaded with medication, requiring the user to carry a separate medical vial. Syringes also require a degree of dexterity and sufficient visual acuity on the part of the patient to line up the needle of the syringe with the rubber septum on the medical vial and to ensure that the syringe is loaded with the proper dosage. As a result, unintentional needle pricks commonly occur.
To overcome the drawbacks of syringes, medication delivery pens have been developed, which facilitate the self-administration of medication such as insulin. Such delivery pens use prepackaged insulin and may be used repeatedly until the medication is exhausted. Mechanical and electronic pens are available. Electronic pens incorporate electronic circuitry that sets and/or indicates the appropriate dosage of insulin and stores data for subsequent downloading such as the time, date, amount of medication injected, etc.
In additional to downloading data, the electronic capabilities of such pens can also be used to mechanically simplify the pen and enhance the pen's ease of use. For example, some known pens employ an interlock mechanism to prevent actuation of the injection button when the medication cartridge is not properly connected to the pen so that an overdose does not occur. The interlock mechanism is relatively complex from both a mechanical perspective and a patient perspective. The electronic detection of the presence or absence of a properly connected cartridge can eliminate the need for such an interlock.
Additional mechanical improvements to medication delivery pens are also desirable to increase reliability and ensure that the proper dosage of medication is delivered. For example, known pens must undergo a priming process every time they are loaded with a cartridge. Priming ensures that the drive mechanism is in contact with the piston inside the cartridge so that the full axial travel of the drive mechanism is used to inject medication rather than being used in part to approach and contact the piston. If priming is not properly performed by the user, the actual dosage of medication that is delivered will not equal the desired dosage. Accordingly, there is a need to eliminate or reduce the amount of priming that the user must perform.
SUMMARY OF THE INVENTION
The subject invention relates to an electronic medication delivery pen which has mechanical features that reduce the amount of priming that must be performed, eliminates the need for an interlock mechanism to prevent overdosing, increases the reliability of the drive mechanism, and ensures that the full dosage of medication is delivered upon injection.
In accordance with the present invention, a medication delivery pen includes a housing having opposing proximal and distal ends. An actuator is disposed in the proximal end of the housing for setting and administering a dosage of medication. A medication-containing cartridge assembly includes a cartridge having a pierceably sealed distal end, an open proximal end removably attachable to the distal end of the housing, and a piston in sliding, fluid tight engagement within the cartridge. A drive mechanism is coupled between the actuator and the cartridge to exert an axial force on the piston to inject the set dosage of medication. The actuator triggers the drive mechanism to administer the injection of medication held in the cartridge. A processor is coupled to the actuator to determine a value equal to the dosage set by the actuator and a memory device is coupled to the processor to store the dosage value determined by the processor. The drive mechanism includes a pair of half nuts in rotational engagement with the actuator, a non-rotatable lead screw having a distal end for exerting the axial force on the piston to inject the set dosage of medication, a proximal end, and threads extending between the proximal and distal ends. The nuts open and close radially to selectively engage with the threads of the lead screw for axially advancing along the lead screw upon rotation of the actuator.
Because the half nuts advance along the lead screw, thus eliminating the need for a rotatable lead screw, the inventive medication delivery pen advantageously reduces the likelihood that components will improperly engage with one another due to their misalignment during operation.
In accordance with another aspect of the invention, a first spring is provided in the housing to bias the lead screw in the distal direction so that the lead screw remains in contact with the cartridge piston when the cartridge assembly is attached to the housing. This feature advantageously reduces the amount of priming that must be performed upon installation of a new cartridge.
In accordance with yet another aspect of the invention, a release nut is provided to engage with the lead screw at a location distally of the half nuts. The release nut is located at a first axial position when the cartridge is attached to the housing and a second axial position when the cartridge is removed from the housing. The release nut activates the processor so that the processor is in an operational state when the release nut is in the first axial position and is in a disabled state when the release nut is in the second axial position. Accordingly, since the pen will be automatically disabled when the cartridge is not properly inserted, the present invention advantageously avoids the need for a separate interlock mechanism.
In accordance with yet another aspect of the invention, at least one dial stop element couples the distal ends of the half nuts to the release nut so that the axial travel of the half nuts is limited to a minimum value, thereby limiting the injectable dosage of medication to a minimum value. Likewise, the dial stop element may also limit the axial travel of the half nuts to a maximum value, thereby limiting the injectable dosage of medication to a maximum value.
In accordance with another aspect of the invention, the actuator includes a rotatable knob and a plunger in rotational engagement with the rotatable knob. The plunger has a plurality of axial splines located on its distal end that define slots therebetween. The housing has at least one radially extending boss that aligns with the slots in select rotational states of the plunger to allow axial motion of the plunger and misaligns with the slots in other rotational states of the plunger to prevent axial motion of the plunger. The select rotational states of the plunger aligning with the boss correspond to an integer number of dosage units. This feature of the invention advantageously ensures that the user can only inject a whole number of units of medication.


REFERENCES:
patent: 5279585 (1994-01-01), Balkwill
patent: 5593390 (1997-01-01), Castellano et al.

Affiliated with

Also associated with

Rating

Medication delivery pen does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Medication delivery pen, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Medication delivery pen will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2461951