Single Stack Monitor for Packaged Medication

Another means of dispensing strips of packaged medication would be to dispense the strips one at a time from a stack of strips. Each strip would contain one dose of medication that is usually taken once per day. As one medication containing strip is dispensed, the stack would move down as shown in these drawings so that the next strip would be in a position to be dispensed.

In the dispenser shown in Figure 1, the blister portions of the strip to be dispensed protrude into an open channel from which they can easily be pushed upon to slide the strip out of the dispenser.

The edge portion of that strip which is in a position to be dispensed is supported on a pair of lips along which the strip slides as it is being dispensed.  As the strip of medication is dispensed, it passes through a sensing channel where it rotates a gate, which causes a switch to be activated to sense the dispensing event. Figures 2 and 3 illustrate in detail how this gate could operate. In Figure 2 the strip, which is being dispensed has not reached the gate. Thus, the gate is held in its "closed" position by the action of its spring. A pair of projections on the edges of the gate press against a switch-operating fork, as shown, causing the fork to depress the button of the switch which senses medication removal.

When the strip passes over the gate, as shown in Figure 3, the gate rotates so that its projections no longer press against the sides of the switch-operating fork. Without the force applied by the gate, the spring within the switch is able push the fork away so that the switch contacts can close to create a signal indicating medication removal. The design of the gate permits the gate to swing part way into the spaces between blisters so that once the first blister has passed the gate, the gate acts as a ratchet preventing the strip from being pushed back into the dispenser.

The gate can be designed to work with strips of packaged caplets containing the four-drug combination distributed by the Global Drug Facility (GDF) at WHO for use in the initial phase of TB therapy. The gate could also work with strips of packaged tablets of the two-drug combination used in the continuation phase if the package now distributed by the GDF was modified. The package for the two-drug combination would have to be redesigned to provide strips of a compatible width with the wider and more closely spaced blisters used in the initial phase. The package would need to have flat blisters to assure stability of the stack. This is shown in Figure 4a.

Since the two-drug combination tablet probably doesn't require protection against moisture, a package that could be filled in the clinic could probably be used for this medication. Such a package is shown in Figure 4b, which has an attached lid with adhesive around the edges that is covered with release paper. The staff could fill the cavity with two to five tablets depending on the weight of the patient, remove the release paper, and attach the lidding to the cavities. This type of package could be used for any medication including HIV medications that do not require protection against ambient moisture.

Since the four-drug combination caplet is about twice as thick as the two-drug combination tablet, the dispenser could accommodate a two-week supply of the four drug combination caplets for the initial phase of therapy when the patient needs to be seen frequently, and a 4 week supply of the two drug combination tablets for the continuation phase of therapy when the patient can be seen less frequently.

Figure 5 shows further details of a possible dispenser design. As shown, a compression plate holds the stack in position and moves downward as medication is removed. Since the patient can be given anywhere between 2 to 5 caplets or tablets per day depending on the weight of the patient, the strips will be different lengths and the compression plate needs to be constrained to prevent it from tipping when the strips are short. As shown in Figure 5, this is achieved by having each end of the compression plate attached to a wide band of thin material which passes over rollers arranged so that the band always moves the two ends of the compression plate the same distance. The force which presses the compression plate against the stack is supplied by a constant force spring connected to the end of the band.

As shown in Figure 6, the barrier can be positioned by tabs, which are located on the ends of a pair of horizontal extensions, which extend perpendicular to the moveable barrier. These tabs engage any of a series of locating notches on one side of a slot which accommodates the pair of horizontal extensions. A leaf spring which is molded as part of the moveable barrier, as shown, acts against the opposite face of this slot to press the tabs into the locating notches. In this design rotating the moveable barrier, as shown in Figure 7, causes the spring to be deflected and the tabs released from their locating notch, as shown in Figure 8. This permits the moveable barrier to be moved to a different location to fit strips of a different length.

In order to move the barrier, the clinic worker would grip the barrier between the thumb and forefinger, rotate it to disengage the tabs, and slide it to its new location. Gripping the barrier could be achieved readily if the side wall of the dispenser was opened to reload the device. It could also be gripped if the bottom of the device was opened so the lips which support the medication packages did not restrict access to the barrier. In this latter case pushing the compression plate upward would allow for a better grip on the barrier.  

When strips of medication are present in the dispenser, they prevent the moveable barrier from being rotated and thus prevent the movable barrier from being repositioned while the dispenser is in use.

Also, since the strips can be different lengths, the dispenser incorporates a moveable barrier which establishes the size of the space occupied by the strips as shown in Figure 5.

Figure 9:  Double Stack Monitor for Strips of Packaged Medication

Figure 10 illustrates one possible design for a monitor of the type shown in Figure 9. Sensing gates similar to the gate described for the single stack monitor could be used to close a switch as each strip of medication is removed. Traces on a circuit board connect each of two switches (one for each of the two stacks of strips) to an electronic unit, which records the time of medication removal. Compression plates push successive strips of medication into position to be dispensed.

To accommodate strips of blister packages of different lengths, i.e. with 2, 3, 4 and 5 packages, this monitor also incorporates a moveable barrier, which is positioned to define the space occupied by the stacks of strips. Figure 11 shows an open view of one side of the device to illustrate a proposed design of this movable barrier.  The movable barrier has a long slit which divides it into two barriers, one for each stack of strips.  The slit fits over the central wall separating the two stacks. At the top of the central wall and at the bottom of the device are a series of locating grooves. The top edge of the slit in the movable barrier fits into grooves along the top edge of the central wall. The lower edge of the movable barrier fits into the grooves at the bottom of the device. The barrier can be moved to the proper grooves for the number of blister package being dispensed by lifting it and moving it laterally and letting the spring pad force the barrier down into the chosen set of grooves. The grooves are deep enough so that the barrier will remain in the grooves if the patient's finger or implement hit the barrier as a strip of packages is being removed.

In the double stack monitor there would be two separate gates similar to the gate shown in Figures 2 and 3. Each gate would activate a switch to detect removal of medication from its stack.  

POTENTIAL AND EXISTING MEDICATION MONITOR DESIGNS

I.   Cover and Cap Opening Monitors

 II.  Dose Removal Monitors

DISPLAYS INCORPORATED INTO COMPLIANCE MONITORS