WO1998048874A1 - Medical inhaler with thermochromic gauge - Google Patents

Abstract

This invention is a metered dose inhaler (10) having a thermochromic display (19) responsive to the temperature changes in the inhaler due to expansion of propellant (26) upon dispensing. Thermochromic display is for the number of doses remaining, amount of medicament in container, etc.

Description

MEDICAL INHALER WITH THERMOCHROMIC GAUGE

This application claims the benefit of Provisional Patent Application Serial No.

60/045401, filed April 30, 1997.

This invention relates to the measurement of doses remaining in sealed medical

containers, specifically to such containers which are used for administering medical compounds.

Members of the medical community commonly prescribe and use sealed containers full

of medication to assist in the treatment of various ailments. These sealed containers are commonly

referred to as Metered Dose Inhalers (MDI's). They are used by a person to inhale exact amounts

of a specified medication into the person's respiratory system.

Because MDI's are mostly made of opaque or translucent materials, it can be difficult to

judge the amount of medication left in them. Manufacturers and members of the medical

community that prescribe and use MDI's commonly recommend that persons using MDI's gauge

the amount of medication remaining and/or lacking in an MDI by floating the MDI container in a

pool of standing water. The amount of medication remaining and/or lacking can be determined by

the buoyancy of the MDI container. However, many consumers object to this method because the

indication given is only vaguely accurate and because it is not always easy to find the time or the

place to float the container. It has also has been proven that exposing the valve stem of an MDI

container with certain medications in it, to liquid, can cause the valve stem to clog, rendering the

MDI ineffective.

Because of these objections, inventors created several different ways of gauging the

amount of medication remaining and/or lacking in an MDI.

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SUBST1TUTE SHEET (RULE 26) U.S. Patent No. 4,817,822 to Rand (1989) discloses a device that "counts" the number

of doses used in an MDI by counting one actuation every time the MDI container is depressed. This

device, however, is comparatively expensive to manufacture, and may easily be reset by accident,

causing the user to lose count of the doses left. It can be costly to replace if lost, especially when

the user has multiple MDI's. Other patents issued that use the basic principle of counting by the

number of depressions include U.S. Patent No. 5,020,527 to Dessertine (1991), U.S. Patent No.

5,363,842 to Misholevich (1994), U.S. Patent No. 5,411,173 to Weinstein (1995), U.S. Patent No.

5,482,030 to Klein (1996), U.S. Patent No. 5,564,414 to Walker (1996) and U.S. Patent No.

5,718,355 to Garby (1998). All of these patents describe devices that depend on the counting of

depressions for determining the number of doses used or left. They all vary in cost of production

and features available; some feature electronic memory, others feature alerts to warn of minimal

doses remaining, and still others feature timers between doses. All of them are either designed to

be integrated with the mouthpiece or connected directly to the MDI container itself.

U.S. Patent No. 5.676,129 to Rocci (1997) also uses a counting method. Although it

does not count the number of depressions, it uses a miniature pressure sensor and microprocessor

to detect the pressure of the MDI container.

All of the devices to determine the amount of medication left in a container heretofore

known suffer from a number of disadvantages:

a) They are comparatively much more expensive to manufacture, especially the ones that

use sophisticated electronics and/or microprocessors.

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SUBST1TUTE SHEET (RULE 26) b) They can possibly be reset accidentally, some perhaps quite easily. This may

cause them to lose count of the number of doses left possibly endangering the user's health.

c) Because none of them are integrated with the MDI container and are generally

not included in the package by the MDI's manufacturer, they must be purchased separately. Along

with the cost of the MDI (which can be quite high if it is a prescribed MDI and the user is

uninsured), the user must pay the additional cost of the measuring device itself, which can be very

high for those using multiple types of MDI's at the same time.

d) Because none of them are generally included in the package by the MDI's

manufacturer, if lost or misplaced, the user must again pay to replace the MDI and pay the purchase

price for a new measuring device, which again can be very high for those using multiple types of

MDI's at the same time.

Although thermochromic technology has been used to determine compound levels in

larger containers such as propane tanks and detergent containers, it has never been used for

determining the number of doses remaining in medication containers. U.S. Patent No. 3,696,675

to Gilmour ( 1972) described a method and means using thermochromic technology to gauge the

difference in temperature between two different compounds in a single container via the difference

in color of the parts of the gauge. The gauge is externally heated and then cooled, which shows

where the different compounds are located on the inside of the container. U.S. Patent No. 4,358,955

to Rait (1982) references improvements to Gilmour's patent by means of the addition of a magnetic

backing that will allow the device to be moved to or from multiple containers. Rait's patent refers

to propane tanks for backyard grills and heating units plus cooking stoves for recreational vehicles. U.S. Patent No. 5,323,652 to Parker (1994) describes a device that works in much the same way as

Gilmour's and Rait's with the exception that it uses a heating means activated by electric current.

The current heats the gauge and causes the color change. Parker's patent also references propane

tanks for gas grills. U.S. Patents Nos. 5,385,044 (1995) and 5,707,590 (1998) both to Thomas, are

for a device that uses thermochromic technology specifically for detecting the amount of detergent

in a plastic opaque container by exposing the thermochromic material to a warm water spray.

Summary of the Invention

According to the invention a thermochromic medication gauge is a device that uses

thermochromic compound(s) to detect the ambient temperature difference between the medication

and propellant inside a metered dose inhaler (MDI) container.

Accordingly, several objects and advantages of the present invention are:

a) To provide a gauge that is comparatively much less expensive to manufacture;

b) To provide a gauge that cannot possibly be reset;

c) To provide a gauge that is integrated with the MDI container in the package; and

d) To provide a gauge that is easier and less expensive to replace if lost.

Further objects and advantages are to provide a gauge that can be easily and conveniently

used without confusion to the user, which can be cheaply manufactured and sold, which can be used

with all types of MDI's repeatedly throughout the useful life of the MDI, which cannot accidentally

be reset, and which can be integrated into the package of the container by the manufacturer allowing

the replacement cost to be lowered if the MDI is lost or misplaced. Still further objects and

advantages will become apparent from a consideration of the ensuing descriptions and drawings.

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SUBST1TUTE SHEET (RULE 26) Description of the Drawings

Figure 1 is a front view of an MDI container with a thermochromic gauge aligned on its

side, and with a portion of the container broken away.

Figure 2 is an enlarged side or cross-sectional view of a thermochromic gauge.

Figure 3 is a side view of a complete MDI with a thermochromic gauge and partially

broken away to show some of its internal parts.

Detailed Description of the Invention

An embodiment of the present invention is illustrated in Figures 1 and 2. An MDI 10

includes a medication gauge 19, which is an elongated strip of plastic material 27 which may be

decoratively colored as, for example, with chrome Mylar®. Gauge 19 has a backing of pressure

sensitive adhesive 28 which must be a good heat conductor. Secured to the surface of the material

27, on the opposite side from the adhesive backed surface 28, is a thermochromic layer 32 secured

thereto by a heat conducting adhesive 30. The thermochromic layer 32 may be in the form of an

ink, paint or other such composition. The thermochromic layer 32 may be liquid crystal and may

comprise a base layer of polymeric film 33 or other suitable plastic material coated with

thermochromic compound(s) imbedded in or incorporated on the polymeric film 33. To enhance

the optical properties of the thermochromic layer 32 a black or dark coating 34 may be utilized to

cover the thermochromic layer 32. This may be ink, a black lacquer or other dark pigmented

coating material. Thus, the polymeric film 33 coated with thermochromic compound(s) or

encapsulated thermochromic compound(s) and backed by a dark coating 34 form the thermochromic

layer 32. For the benefit of the user, polymeric film 33 may have printed in or on its surface, doses remaining graduations 19(a), a full container graduation 19(b), a refill container graduation 19(c)

and an empty container graduation 19(d) or other marking leading to the same result for the same

purpose. In the preferred embodiment, the thermochromic compound used is available from Matsui

Corporation of Gardena, California. See, for example; Table I in U.S. Patent 5,707,590 to Thomas

et al. However, the thermochromic layer 32 can consist of any other compound that can detect and

display temperature changes by changes in color.

Because ultraviolet radiation has been proven to deteriorate and diminish the chromic

characteristics of thermochromic compounds, the medication gauge 19 may include an additional

layer over the thermochromic layer 32. This may be in the form of an optically transparent

ultraviolet filter layer 36 such as "Tedlar," available from E.I. duPont de Nemours, Inc., described

in its Bulletin PD-5, March 1971.

The method of production in the preferred embodiment may include using multiple

thermochromic compounds that work at different temperature ranges on the elongated strip. This

practice may be beneficial because using multiple thermochromic compounds that work at different

temperature ranges allows for more accurate readings and the ability to effectively give a reading

when the container is subjected to temperatures outside of the ideal room temperature range. These

temperatures could possibly range from -50 degrees F to +120 degrees F, depending on seasonal

climate and geographic location. The method of production in the preferred embodiment may also

include having the medication gauge 19 placed on the container 10 in intimate heat transfer relation

to the outer side of the container wall 20 in a height- wise position by the manufacturer in a manner

that accurately aligns the graduations 19 (a), 19(b), 19(c), and 19(d) on the strip with the medication level inside the container 10, and may include incorporating the medication gauge 19 into the design

of the product label itself.

Another embodiment may include using multiple thermochromic compounds that work

at different temperature ranges for the same reasons. The difference of the production methods

would be that the thermochromic compound used may be placed in the materials that comprise the

container 10 itself during their production. For example, if the container is comprised of metallic

materials, the thermochromic compound(s) used may be integrated into the metallic materials while

they are being produced before they are formed into the container 10. The container 10 would then

be coated or embedded with a optically transparent ultraviolet filter 36 layer much like the

elongated strip and would also have the graduations 19(a), 19(b), 19(c), and 19(d) printed on it in

a manner viewable by the user, much like the preferred embodiment. This method can also be used

with containers made of other types of materials such as plastics or glass.

The method of operation is illustrated in Figures 1 and 3. An MDI is used by placing

container 10 into a casing 16 and securing a valve stem 12 of the container 10 to a valve control 14

of the casing 16. The user then seals his or her lips around a mouthpiece outlet 18 of the casing 16

and compresses the container 10 downwards, allowing the valve stem 12 of the container 10 to open

and release a specified amount of medication through the control valve 14 of the casing 16, which

directs the flow of medication through the mouthpiece outlet 18 of the casing 16. The user then

inhales the released medication. Use of the medication gauge 19 is made possible by the reaction

inside the container 10 during the process of compression. The container 10 is filled with two basic

components under pressure. One is a medication 24, which may be in the form of a liquid or solid

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SUBST1TUTE SHEET (RULE 26) granular flowable form. The second component is a propellant 26, which may be a liquid, a gas or

a combination of both. The separation point between the two components is at an interface 22 and

is the indication point of the level of medication in the container 10. When the container 10 is

compressed downward to release the medication, the pressure in the container 10 drops, causing the

ambient temperature of components to vary in such a way that the thermochromic compound in a

heat-transfer-sensitive relationship to the outside of the container detects the difference in

temperature between the propellant 26 and the medication 24. The detection of the temperature

difference is visible to the user, when holding the MDI in an upright position, in the form of a color

difference between the two components. The point at which the medication gauge 19 changes color

is an accurate representation of the location of interface 22 inside container 10. Thus, by

compressing the container 10 downwards, the user can then view through a cut out 17 in casing 16,

an accurate determination of the number of doses remaining can be made using graduations 19(a).

The user can also determine if the container is full 19(b), needs to be refilled 19(c), or is empty

19(d).

Another method of operation may include using an outside source to create the

temperature change of the thermochromic compound(s). This could be accomplished by heating

or cooling the thermochromic compound(s) with a hot or cold liquid such as water and then waiting

for the container 10 to warm up or cool down to show the color change and thus the level of

medication. With this method of operation, the user would remove the container 10 from the casing

16 and place it in a pool or stream of hot or cold water. When a color change is observed, the user

would remove the container 10 from the water while making sure to hold it upright and wait for it to change back to its original color. During this period the point at which the medication gauge

changes color, is where the interface 22 is. Thus giving the same results as the preferred method

of operation mentioned above.

Claims

I claim:

1. A metered dose inhaler having a container enclosing a medication to be delivered

to a user and a propellant, and having improved and simplified means for dose counting, the

improvement comprising:

an elongated strip of material adhered to the metered dose inhaler;

a thermochromic layer adhered to a surface of the elongated strip, the thermochromic

layer being responsive to temperature change of the propellant within the container resulting from

the expansion of the propellant when a dose of medication is delivered, whereby at least a portion

of the thermochromic layer changes color in response to the changed propellant temperature

indicating the interface of the remaining medication and the propellant; and

graduations on the thermochromic layer and visible to the user, the graduations and color

change cooperating to indicate the approximate location of the interface between the remaining

medication and the propellant whenever the inhaler is actuated.

2. A method for counting the number of doses remaining in a metered dose inhaler

containing a medication and a propellant, the method comprising the steps of:

compressing the metered dose inhaler to release a dose of medication;

sensing and indicating a temperature change of the propellant by thermochromic

detection on a strip in contact with the side of the metered dose inhaler;

indicating by different colors on the strip a location of an interface between two regions

of different temperature inside the metered dose inhaler; and comparing the location of the interface to quantity graduations on the container or strip o determine the number of doses remaining.

3. A thermochromic gauge for a medical inhaler, comprising:

a medication container;

a strip of material adhered to the medication container;

a thermochromic layer adhered to the strip of material;

a plurality of graduations on the thermochromic layer, the graduations indicating the

quantity of medication remaining in the container;

4. The thermochromic gauge of claim 3, where the strip of material is adhered to

the medication container by a heat-conductive adhesive;

5. The thermochromic gauge of claim 3, where the thermochromic layer is adhered

to the strip of material by a heat-conductive adhesive.

6. The thermochromic gauge of claim 3, where the strip of material is adhered to

the medication container along a longer axis of the container.

7. The thermochromic gauge of claim 3, further comprising an optically transparent

filter layer covering the thermochromic layer.

8. The thermochromic gauge of claim 3, further comprising a layer of dark-

pigmented lacquer covering the thermochromic layer.

9. The metered dose inhaler of claim 2, wherein the method further comprises:

determining the approximate location of the interface without the use of a water bath, or

external source of heat.