Method of testing the dose accuracy of a medication delivery device

A method for testing the accuracy of a medication delivery device, such as a medication delivery pen, includes the steps of: PA1 a) providing a syringe assembly having a hollow barrel with volume measuring indicia on the barrel, a slidable stopper in the barrel and a needle cannula at the distal end of the barrel; PA1 b) providing a medication delivery pen having a pierceable septum at its distal end, a reservoir for containing liquid adjacent to the septum, a movable plunger for dispensing liquid from the reservoir projecting from the proximal end of the pen and dose setting apparatus for manually selecting the volume of liquid to be delivered by action of the plunger; PA1 c) manually activating the dose setting apparatus to select the volume of liquid to be delivered from the pen; PA1 d) piercing the septum of the pen with the needle cannula of the syringe; PA1 e) activating the plunger to dispense the selected volume of liquid from the reservoir through the needle into the syringe barrel chamber so that as liquid enters the chamber the stopper is moved proximally along the syringe barrel chamber; PA1 f) observing the volume of liquid dispensed into the syringe barrel chamber.

FIELD OF THE INVENTION 
The subject invention relates to medication delivery pens and a test method 
for determining the dose accuracy of medication delivery pens. 
DESCRIPTION OF RELATED INFORMATION 
Hypodermic syringes are used to deliver selected doses of medication to 
patients. Generally speaking, a hypodermic syringe includes a cylindrical 
syringe barrel having an open proximal end and a distal end. The barrel 
includes a cylindrical wall between the distal and proximal ends which 
defines a fluid receiving chamber. The proximal end of the barrel receives 
a stopper in fluid-tight engagement. A plunger rod extends proximally from 
the stopper out of the open proximal end of the barrel. The distal end of 
the barrel includes a passage communicating with the chamber. A needle 
cannula may be mounted to the distal end of the syringe barrel such that 
the lumen of the needle cannula communicates with the passage and the 
chamber of the syringe barrel. Movement of the plunger in a proximal 
direction draws fluid into the lumen of the needle cannula and into the 
chamber. Movement of the plunger in a distal direction urges fluid from 
the chamber and through the lumen of the needle cannula. 
Medication to be injected with a prior art hypodermic syringe often is 
stored in a vial having a pierceable elastomeric septum. Medication in the 
vial is accessed by piercing the elastomeric septum with the needle 
cannula. A selected dose of medication may be drawn into the chamber of 
the syringe barrel by moving the plunger a selected distance in a proximal 
direction. The syringe barrel typically contains volume measuring indicia 
which allows the user to accurately measure the amount of liquid drawn 
into the barrel. The needle cannula may be withdrawn from the vial, and 
the medication may be injected into the patient by moving the plunger in a 
distal direction. 
Some medication, such as insulin, is self-administered. The typical 
diabetes patient will require injections of insulin several times during 
the course of a day. The required dose of insulin will vary from patient 
to patient, and for each patient may vary during the course of the day and 
from day to day. Each diabetes patient will establish a regimen that is 
appropriate for his or her own medical condition and for his or her 
lifestyle. Each of these regimens may require the diabetes patient to 
periodically self-administer insulin in public locations, such as places 
of employment or restaurants. The required manipulation of the standard 
prior art hypodermic syringe and vial can be inconvenient and carrying 
vials and syringes can be embarrassing in these public environments. 
Medication delivery pens have been developed to facilitate the 
self-administration of medication. One prior art medication delivery pen 
includes a vial holder into which a vial of insulin or other medication 
may be received. The vial holder is an elongate generally tubular 
structure with proximal and distal ends. The distal end of the prior art 
vial holder includes mounting means for engaging a double-ended needle 
cannula. The proximal end also includes mounting means for engaging a pen 
body which includes a driver and dose setting apparatus, as explained 
further below. A disposable medication containing vial for use with the 
prior art vial holder includes a distal end having a pierceable 
elastomeric septum that can be pierced by one end of a double-ended needle 
cannula. The proximal end of this vial includes a stopper slidably 
disposed in fluid tight engagement with the cylindrical wall of the vial. 
This medication delivery pen is used by inserting the vial of medication 
into the vial holder. A pen body then is connected to the proximal end of 
the vial holder. The pen body includes a dose setting apparatus for 
designating a dose of medication to be delivery by the pen and a driving 
apparatus for urging the stopper of the vial distally for a distance 
corresponding to the selected dose. 
The user of the pen mounts a prior art double-ended needle cannula to the 
distal end of the vial holder such that the proximal point of the needle 
cannula pierces the septum on the vial. The patient then selects a dose 
and operates the pen to urge the stopper distally to deliver the selected 
dose. The dose selecting apparatus returns to zero upon injection of the 
selected dose. The patient then removes and discards the needle cannula, 
and keeps the prior art medication delivery pen in a convenient location 
for the next required medication administration. The medication in the 
vial will become exhausted after several such administrations of 
medication. The patient then separates the vial holder from the pen body. 
The empty vial may then be removed and discarded. A new vial can be 
inserted into the vial holder, and the vial holder and pen body can be 
reassembled and used as explained above. 
The above description describes a reusable medication delivery pen. 
Delivery pens may also be disposable. Disposable pens are discarded after 
the reservoir having the pierceable septum is emptied of its contents. In 
other respects their operation is similar to the description above. 
A medication delivery pen such as an insulin pen provides many advantages 
to the active diabetic who must carry his medication delivery equipment 
with him throughout the day. The pen offers a self-contained mechanism for 
insulin administration. Insulin pens are well known in the art and are 
described in many patents. Most insulin pens use a double-ended needle 
having a threaded hub which engages the distal end of the pen and while 
simultaneously piercing the septum of the insulin reservoir. 
The vast majority of all insulin is delivered through single-use plastic 
disposable syringes. Unlike the syringe, with the insulin pen it is not 
obvious if the correct dose has been injected, or if any insulin has been 
injected at all. The proper performance of insulin pens is critical to the 
well-being of the patient with diabetes. To date there is no known simple, 
accurate and economical method for a diabetic to verify the dose delivery 
of an insulin pen. One manufacturer provides a needle shield with a 
graduation line for a specific number of units of insulin. The user is 
instructed to inject the insulin through the needle into the cavity of the 
needle shield. A disadvantage of this method is that after the insulin is 
injected into the needle shield it must be thrown out. Insulin is 
expensive and providing an expensive test may discourage users from 
frequently checking their insulin delivery pens. Also, when the insulin 
delivered is more or less than the volume indicated by the line on the 
receptacle the user does not know how much more or how much less or if 
this amount is significant. 
Accordingly, although the art teaches many medication delivery pens such as 
insulin delivery pens, both reusable and disposable, there still does not 
exist a simple, easy-to-use, economical method of testing the dosage 
accuracy of a medication delivery pen. 
SUMMARY OF THE INVENTION 
A method for testing the dose accuracy of a medication delivery device 
includes the steps of: 
a) Providing a syringe assembly having a hollow barrel with volume 
measuring indicia on the barrel. The barrel includes an internal chamber, 
a stopper slidable in the chamber, and a needle cannula at the distal end 
of the barrel having a lumen therethrough in fluid communication with the 
chamber. 
b) Providing a medication delivery pen of the type using a needle assembly 
having a hub and a needle held by the hub so that both ends of the needle 
protrude from the hub. The pen has a distal end including a pierceable 
septum and means for engaging the double-ended needle assembly so that one 
end of the needle pierces the septum. A reservoir is contained within the 
pen adjacent to the septum. A movable plunger for delivering liquid from 
the reservoir projects from the proximal end of the pen. Dose setting 
mechanism is provided for manually selecting the volume of liquid to be 
delivered by action of the plunger. 
c) Manually activating the dose setting mechanism of the pen to select the 
volume of liquid to be delivered from the pen. 
d) Piercing the septum of the pen with the needle cannula of the syringe so 
that the lumen of the needle cannula is in fluid communication with the 
reservoir of the pen. 
e) Activating the plunger to dispense the selected volume of liquid from 
the reservoir through the lumen into the syringe barrel chamber so that as 
liquid enters the chamber the stopper is moved proximally along the 
chamber. 
f) Observing the volume of liquid dispensed into the chamber. 
After the accuracy of the medication delivery device is measured, the 
liquid in the syringe can be injected into a patient. Some syringes may 
come with their stoppers positioned at various distances from the distal 
end of the syringe. To perform this test most accurately, the stopper 
should be moved distally to attempt to eliminate any air volume in the 
graduated portion of the barrel.

DETAILED DESCRIPTION 
While this invention is satisfied by many different steps and sequences, 
there is shown in the drawings and will herein be described a preferred 
method of the invention with the understanding that the present disclosure 
is to be considered exemplary of the principles of the invention is not 
intended to limit the invention to the specific method illustrated. The 
scope of the invention will be measured by the appended claims and their 
equivalents. 
Adverting to FIGS. 1-6 a prior art hypodermic syringe assembly 20 includes 
an elongate hollow barrel 21 having a chamber 22 for retaining liquid. 
Barrel 21 includes open proximal end 23, distal end 25 and a tip 27 
extending from the distal end and having a passageway therethrough in 
fluid communication with chamber 22. A needle cannula 28 extends distally 
outwardly from the tip and includes a lumen therethrough in fluid 
communication with the passageway. 
For the purposes of the description of the present invention the term 
"distal end" is mean to refer to the end of the syringe closest to the 
needle and the end of the medication delivery pen closest to the 
pierceable septum while the term "proximal end" is mean to refer to the 
end of the syringe furthest from the needle and the end of the medication 
delivery pen from which the plunger extends. 
Syringe 20 also includes an elastomeric stopper 31 slidably positioned in 
fluid-tight engagement inside barrel 21. The stopper is capable of moving 
fluid from chamber 22 through the passageway of the needle upon its 
movement toward distal end 25 of the barrel. The stopper is also capable 
of facilitating drawing fluid into the chamber through the passageway upon 
its movement away from distal end 25 of the barrel. A plunger rod 32 
having an elongate body 33 engages stopper 31 to facilitate operation of 
the stopper. Body portion 33 extends outwardly from open proximal end 23 
of the barrel. Disc-shaped plunger rod flange 34 is provided as a 
convenient structure for applying force to the plunger rod with respect to 
the barrel. 
Some diabetics prefer to self-administer insulin using medication delivery 
pens such as medication delivery pen 37. Medication delivery pens are well 
known in the art and are taught in U.S. Pat. Nos. 4,498,904 and 4,973,318. 
Many medication delivery pens use a disposable needle assembly having a 
threaded hub and a double-ended needle cannula. Such a needle is discussed 
in U.S. Pat. No. 5,015,235 which teaches a needle package. As best 
illustrated in FIGS. 2 and 3, a prior art needle assembly 38 includes a 
cylindrically shaped hub 39 and needle cannula 40 having projecting distal 
end 41 and proximal end 43. Distal end 41 includes a sharpened tip 44 for 
injection of medication into the patient and, in this example, a sharpened 
tip 45 at proximal end 43 for piercing the septum of the pen liquid 
reservoir. 
A typical reusable pen will use medication vials such as vial 46 having a 
pierceable septum 47 at its distal end. Vial 46 includes open proximal end 
49 and interior cylindrical chamber 50 containing medication as 
illustrated by liquid 5 1. A resilient stopper 52 occludes pen proximal 
end 49 of the vial and is slidably movable within the vial and functions 
in the same manner as the syringe assembly stopper previously described. 
When all of the liquid in the vial is dispensed, the vial is thrown away 
and a new vial is used in its place. 
Pen 37, in the illustrated pen, includes transparent removable vial holder 
55 having a threaded distal end 56 adapted to engage internal threads 57 
of needle hub 39. The transparent vial holder also includes a threaded 
proximal end 57 which screws into complementary threads in main body 58 of 
pen 37 to firmly hold and position the medication vial. 
In use, a vial of liquid such as insulin is placed in the medication 
delivery pen and a disposable double-ended needle such as needle assembly 
38 is attached to the distal end of the pen. As illustrated in FIG. 4, the 
user sets the dose by rotating dose selecting knob 59 of the pen until the 
numerical representation of the desired dose appears in window 61. 
Internal mechanism in the pen extends or allows the pen plunger 62 to 
extend proximally when the dose is set. The user then inserts the needle 
into the selected portion of his or her body and depresses plunger 62 
until it travels its full stroke or as far as the pen will allow it to go. 
The needle may then be removed since the dose delivery is complete. In 
many pens the plunger will stay in the depressed position until the next 
dose is selected. Unlike the commonly used syringe, graduations on the 
medication delivery pen, if any, are not suitable for accurate dose 
measurement, so the user must accept, as a matter of faith, that the dose 
numerically represented in window 61 is the dose being delivered by 
depressing plunger rod 62. In cases such as with diabetics, the dose is 
critical to the therapy and providing more or less than the required dose 
can have serious consequences for the diabetic. Accordingly, it is 
important for the user, such as a diabetic, to check his or her pen from 
time to time to assure that an accurate dose of medication or other 
therapeutical liquid is being delivered. 
A prior art method of determining dose involves supplying the double-ended 
needle and hub assembly in a rigid receptacle which has a volume 
indicating line printed on the receptacle. The diabetic will deliver a 
pre-determined dose of liquid, such as insulin, into the receptacle, such 
as 20 units. The line on the receptacle is designed to measure 20 units, 
exactly. The disadvantage of this method is that the insulin used for the 
test must be discarded and the expense of throwing insulin out may 
discourage users from using the test. In addition, if the insulin level is 
above or below the line, the user does not know the magnitude of the 
discrepancy and does not know if it is relevant or irrelevant. 
The method of the present invention provides a simple, easy-to-use method 
for pen users such as diabetics for checking the dose delivered by their 
pen. The method of the instant invention also overcomes the shortcomings 
of known methods described hereinabove. 
The preferred method of the present invention for testing the dose accuracy 
of pen 37 includes the following steps. 
a) Provide a syringe assembly such as syringe 20 having a hollow barrel 21 
with volume measuring indicia 26 along the barrel. The volume of liquid 
contained in the barrel is measured from the distal surface of stopper 31 
using the volume measuring indicia. A typical diabetic syringe, such as a 
1/2 cc insulin syringe for U-100 insulin, contains approximately 50 
graduations so that the volume contained therein can be accurately 
measured. Further details of the syringe have been described hereinabove. 
b) Providing a medication delivery pen, such as pen 37, of the type capable 
of using a double-ended needle assembly to deliver medication. Pen 37 
includes a distal end 64 having a pierceable septum 47 and a reservoir 
containing liquid adjacent to the septum. Although this method can be 
practiced with reusable and disposable pens, the pen illustrated herein is 
reusable and uses a replaceable vial such as vial 46 of FIG. 2 to contain 
the liquid. Pen 37 further includes plunger 62 for delivering liquid from 
the reservoir. Plunger 62 projects proximally outwardly from the main body 
of the pen 58. The pen includes internal (not shown) dose-setting means 
for allowing the user to manually select the volume of liquid to be 
delivered. In the illustrated pen, dose selecting knob 59 is rotated until 
the numerical representation of the desired dose is visible through window 
61. 
c) Manually activating the dose selecting means to select the volume of 
liquid to be delivered from the pen. 
d) As best illustrated in FIG. 6, piercing the septum of the pen with the 
needle cannula of the syringe so that the lumen of the syringe is in fluid 
communication with the reservoir of the pen. 
e) Activating the plunger by applying manual force A to plunger 62 to 
dispense the selected volume of liquid from the reservoir of the pen 
through the lumen of the syringe needle into the syringe barrel chamber so 
that as the liquid enters the chamber, elastomeric stopper 31 moves 
proximally along elongate barrel 21. 
f) Observing the liquid volume dispensed into barrel chamber 22 between the 
distal end of stopper 31 and the distal end of the barrel. The volume will 
be indicated by volume measuring indicia 26. 
If the volume of liquid in syringe 20 is identical to the volume selected 
for delivery from pen 37 the user may now directly self-administer the 
liquid from the syringe to his or her own body. If the pen is delivering 
too much liquid the user may dispose of the additional liquid before 
injection. In addition, also, if the pen is delivering too little liquid 
the user may obtain additional liquid from another source to complete the 
medication regimen. It can be seen that the present method allows the user 
to determine not only if the exact dose set is being delivered but what 
the dose being delivered is in specific units. The user may then discard 
the pen if the delivered dosage is substantially different from the 
selected dose. 
It can be seen that the order of the steps in the method of the present 
invention may be varied so long as the syringe and the pens are connected 
in the manner taught, and the pen is used to drive liquid from the pen 
reservoir into the chamber of the syringe. 
Thus, the present invention provides a simple, easy-to-use method for 
determining the accuracy of a medication delivery pen such as an insulin 
delivery pen while not wasting the medication used for testing the volume 
delivery.