A) Optimal Medication Monitor(s) and Method of Retrieving Adherence Record.
B) Other Dose Removal Monitors.
Stack Type Medication Monitor for Global Drug Facility Packages
NOTE: The this page describes a dispenser which would be used to dispense strips containing the four-drug caplets used in the initial phase of therapy and a second, separate, dispenser which would be used to dispense strips containing the two-drug tablets used in the continuation phase of therapy. The following page discusses how a single, similar dispenser could be used to dispense both medications.
Figure 1 shows the stack monitor with strips of the four drug combination used in the initial phase of TB therapy. The strip extending through the relieved area at the bottom of the dispenser contains the next dose to be dispensed. To dispense this dose, the patient simply pulls out the strip. As the strip is removed the stack of strips moves downward under the action of a compression plate as illustrated in Figures 4 and 5. The lower edge of the side cover shown is positioned so that only one strip can be removed at a time. A transparent portion of this side cover allows the patient to see how much medication is in the dispenser to show the patient when he needs to return for a refill of medication. If the patient does not remember whether today’s medication was taken, he/she presses the Patient’s Query Button. The matrix display then shows a character whose shape and color indicate whether the patient should take a dose of medication.
When the caregiver or member of the clinic staff wishes to review the patient’s adherence record or to refill the dispenser, the side cover is unlatched and removed, as shown in Figure 2. Removing the side cover reveals a Caregiver’s Button which can be used to display the adherence record on the matrix display, as described in the section Using a Dot Matrix display to retrieve the adherence record. The sections Retrieval of the Adherence Record with Audible Tones in the Clinic or Transmitted to the Clinic by Mobile Phones and Retrieval of Adherence Record in Patient’s home using Red/Green/Yellow LED describe other methods which could also be used to retrieve the compliance record. When a computer is available for uploading and displaying the adherence record, the monitor is connected to the computer through a USB cable which plugs into the USB connector which is also located behind the side cover. This USB connection is also used to download patient information into the monitor when the monitor is first filled.
The monitor’s batteries are also located behind the side cover. So, when the cover is removed, the batteries can be replaced if needed. Before the matrix display shows the patient’s adherence record, it displays the battery status so the caregiver or clinic staff will know if the batteries need replacing.
When the dispenser is to be filled, the compression plate is raised, and strips of medication packages are loaded. For the dispenser to operate correctly, the packages must be loaded with their flat side down, as shown.
The dispenser accommodates strips containing 2, 3, 4, or 5 medication units. A positionable barrier within the dispenser is used to adapt the dispenser for these different lengths of strips. The position of this barrier is normally set when the dispenser is first filled for a new patient. To do this, the top cover of the dispenser is first unlocked and removed. Then, the positionable barrier is lifted and moved to the proper set of slots in the sides of the dispenser, as shown in Figure 3 and Figure 4.
Figure 4 illustrates the mechanical elements of the dispenser.
As described above, the positionable barrier adapts the dispenser for strips of 2, 3, 4, or 5 medication units. Note that each side of the positionable barrier has a projection which engages slots in the sides of the dispenser. These slots have tapered entrances to make it easy to engage the barrier into the slots. A bar across the lower end of the positionable barrier is incorporated to stiffen the barrier. This bar serves the added function of retaining the positionable barrier in the dispenser. Before the positionable barrier is repositioned, the compression plate is raised to the top of its travel. This permits the positionable barrier to be lifted and positioned into a different slot. When the positionable barrier is lifted, it cannot be removed from the dispenser because the bar across the lower end of the positionable barrier is retained by the compression plate.
The compression plate which pushes down on the stack of packages is pulled down against the top of the stack by a constant force spring. When the dispenser is in use, a ratchet permits the compression plate to move in only one direction to assure the integrity of the stack of packages when the dispenser is subjected to inertial loads which could overcome the spring force (e.g. if it is dropped when upside down). When the dispenser is to be loaded, the ratchet pawl shown in figures 4 and 5 is released so that the compression plate can be lifted to the top of its travel. There, the pawl can fall into a depression so as to hold the compression plate in position while the dispenser is filled.
Figure 5 shows details of the ratchet and pawl, illustrating how the pawl engages the ratchet. This illustration shows that the the pawl is supported on a pivot and rotated into contact with the ratchet by a spring. A pawl release tab allows the person filling the dispenser to release the pawl from the ratchet so that the compression plate can be raised.
We experimented with a variety of switches to record when a medication package was removed and found problems with all of them. Consequently, we decided that an encoder strip shown in Figure 6 would be better. In order to determine medication removal, the monitor incorporates an encoder as shown in Figure 6. The encoder reports the position of the compression plate, and, hence, the height of the stack of packages to the microcontroller on the monitor’s circuit board. The microcontroller periodically samples the encoder; and when the microcontroller determines that the compression plate has moved enough to represent medication removal, it records the removal event. To ensure that spurious small movements are not recorded as removal events, the encoder can sense differences in position significantly smaller than the thickness of the strip of medication, and the microcontroller can be programmed to ignore small movements. To avoid sensing of apparent large movements when the compression plate, in fact, only moved a small distance, the encoder uses Gray Code in which bits change only one at a time. Thus, the encoder is more reliable than simply sensing a switch closure.
The “fingers” on the compression plate shown in Figure 5 are part of a common strip of metal. Thus, all of the “fingers” are electrically connected. One of them is always in contact with the continuous metal “common” strip on the encoder. The others make contact to those contact strips which present conductive material at the level of the “fingers”. This brings those strips to the same electrical potential as the “common” strip. The pattern of contact strips at the “common” potential is used by the program in the microcontroller to determine the position of the compression plate.
The encoder strip could be made in several ways. One way would employ a circuit board having the contact patterns etched on it.
Positionable barrier raised for repositioning