In-Home Monitoring

Medication Tracking and Reminding Device

Problem

Poor medication adherence is one of the major causes of illness and of treatment failure in the USA. Bedell et. al. [1] found a 76% discrepancy rate between what medicines patients were prescribed, and what medicines they actually took. Furthermore, clinical trials to assess the safety and efficacy of new drugs necessarily rely on proper medication adherence by study participants to obtain accurate data [2, 3]. Thus, accurate assessment of medication adherence is important to patients, caregivers, and researchers.

Existing methods of tracking medication adherence suffer from a number of drawbacks. Pill counts, the mostly commonly used method, overestimate adherence [4, 5]. So does self-report of adherence [5-7]. Existing electronic tracking systems such as the widely-used Medication Event Monitoring System [4] (MEMS, Aardex Ltd.) provide excellent information about adherence, but suffer from several drawbacks. First, the MEMS cap is difficult to open for arthritic hands [8, 9]. Second, MEMS does not report adherence in real time, so intervention cannot take place if medications are missed. Third, MEMS does not accommodate the use of pill boxes for sorting medications into daily doses, as are commonly used by the elderly [10] and when multiple drugs are taken [11, 12].

We have developed a simple electronic medication tracking device based on a standard multi-compartment pill-box that overcomes some of these limitations. In this paper we present an overview of the design of this system, followed by an evaluation of its use in monitoring adherence to a vitamin regimen among community-dwelling seniors. We conclude with a discussion of related work and potential enhancements to the device.

Device Requirements

There were four key requirements driving the design of this device:

• Use a multi-compartment pillbox available at any pharmacy
• Portable at least from room to room, possibly outside the home
• No user interaction required beyond taking the medication
• Daily access to medication adherence data

Prototype Device

Figure 1 shows the outside and inside of the final prototype device, called a MedTracker. The initial device deployed in the field trials described below was susceptible to electrostatic discharge into the PIC reset pin, causing an SCR latchup on the PIC. When this happened, the PIC continued to run, but the battery would drain, and the Bluetooth pairing would sometimes be lost. This problem was corrected in the MedTracker II by adding a 10k resistor and a 0.1µF capacitor at the reset pin. In the MedTracker II we also added a DIP switch for forcing the radio on for initial setup.

Field Trials

Subjects

39 elderly subjects (aged 82.4 ± 5.8 years, 13 men, 26 women) participated in a field study in which we assessed their adherence to a twice daily vitamin regimen using the MedTracker. Subjects were also asked to complete a questionnaire about the usability of the device. All subjects were living independently in townhomes and apartments.

Methods

Subjects were asked to take a single low-dose (250mg) vitamin C tablet twice daily (once in the morning, once in the afternoon) for five weeks, using the MedTracker. Subjects loaded the MedTracker once a week. Data were uploaded via the Bluetooth link from the MedTracker to a computer placed in the home. Collected data were transferred nightly to a central computer through a dial-up connection.

Whenever a subcompartment door changed state, the MedTracker stored the door id, the time since last reset, the current battery level, the number of registered events, the number of successful Bluetooth connections since the last event, the number of failed Bluetooth connections since the last event, and a sequence number. Thus a number of measures of interest could be derived from these data. The time when the device was loaded was determined by identifying those periods in which all 7 doors were opened at least once in a 10 minute period. Single door openings were considered pill-taking events. Opening of the wrong compartment (i.e. the wrong day) was flagged as an error, although as long as at least 1 door was opened at the correct time, we considered a pill to have been taken. We examined three adherence-related measures: percentage of days in which both vitamins were taken; percentage of doses in which vitamins were taken within 1 hour before or 2 hours after the prescribed time (dose time adherence); and number of errors in which the wrong door was opened, indicating confusion about the date. In addition, we recorded the number of failed and successful attempts to transfer data from the device via the Bluetooth link, days of data lost due to MedTracker problems, and difficulties the users had using the device.

Results

38 subjects successfully used the device throughout the 5-week period. The final subject loaded the device once but then forgot to use it thereafter, although she continued to take the vitamins from the bottle, hence her adherence data were excluded from analysis. Two subjects took the device on vacation with them (1 week); when they returned, connection to the computer was automatically reestablished and the data for that week was successfully uploaded. Table 1 shows the results for each of our measures.

1) Device reliability

Overall, the MedTracker performed well in the field. Data was successfully transferred every two hours 90.9±14.6% of the time. The first 9 subjects used the MedTracker 1 version of the device, which was susceptible to power surges due to static discharge, resulting in a loss of pairing with the computer and a failure to transfer data. The MedTracker 2 version of the device did not suffer from this problem. Failed transfers accounted for 18.5% of transfer attempts among MedTracker 1 users, versus 4.8% among MedTracker 2 users. Two devices were not retrieved within 8 weeks from the start of their deployment, and ran out of batteries. Also, in the case where pairing of the device with the computer was lost, it was possible to lose data due to a filling of the circular RAM buffer. This occurred in only 2 cases. Out of a total 1330 days of data collected, 29 days of data were lost due to connection failure and filling of the buffer, or to power failure.

2) Usability of the device

All but 1 subject reported that the MedTracker was easy to use, although one additional subject reported difficulty in opening the compartments. 17% of the subjects used a similar pillbox for their own medications. 6 people reported that the size of the device was problematic, as they would have liked to take it with them in their pockets when they were not going to be home to take their vitamin.

3) Adherence to the vitamin regimen

Total adherence was about 79% overall. Pill counts at the end of the study confirmed these estimates. In contrast, subjects’ self-report indicated far better adherence (93% or better on average) than the objective data provided by the MedTracker. Also, 12% of subjects believed they never missed a dose (versus the 5.3% who actually never did). In 27 cases, the pills were taken from the wrong sub-compartment or two compartments were opened, suggesting some confusion about the day of week or about whether or not previous doses had been taken. Thus the MedTracker provided more detailed analysis of adherence issues than would be possible with existing devices.

Discussion

A number of researchers have proposed devices that will improve or assess medication adherence [14, 15]. Wan [14] proposed the “Magic Medicine Cabinet” which used RFID to identify which medications were taken out of a cabinet, face recognition to identify who approached the device, and a broadband connection to be able to provide an integrated “situation health portal”. Thus, users were required to use the medicine cabinet and to store all medications in separate bottles that could be RFID tagged. Fishkin et al. [15] proposed a lighter-weight version of the medicine cabinet, in which RFID tagged bottles were kept on a monitoring pad that incorporated an RFID tag reader and a scale, for determining how much medication had been taken. These comprehensive systems provide for much richer interaction with the user than our MedTracker, but lack portability and the ability to take advantage of the adherence cues of dose-specific compartments. However, a field comparison of the MedTracker to each of these devices still remains to be done to determine if the portability and multi-compartment nature of the MedTracker does in fact improve adherence.

Our current work has a different goal, namely to enable improved assessment of adherence without requiring the user to modify how they take their medications, and to provide a solution that is particularly effective for seniors, who frequently have trouble opening standard pill containers. The portability of the MedTracker is an important feature, since subjects were able to take the device with them when they were traveling. This is particularly important for use in clinical trials, where accurate adherence information throughout the trial is vital to assessing efficacy and side effects of new drugs. The MedTracker also allows the collection of key information about adherence behavior as compared with existing devices. For example, it was possible to identify when incorrect compartments were opened, which could be extremely important in cases where different medications were to be taken on different days.

Clearly, the current MedTracker is not optimized for size, and could be made much smaller. In addition, other form factors could be instrumented in a similar way (such as single-day multi-compartment pillbox, or single week twice-daily pillbox). The immediate availability of data opens the possibility of prompting the user to take medication specifically when they have missed a dose, although it requires that a computer be available in the home to collect and process the data in real time. We are currently working with researchers in Intel Corporation’s Digital Health Group who are developing a context-aware medication prompting system based on a device derived from our prototype.

One drawback of the MedTracker is that although the prototype device itself cost about $200 to make (and could be made for much less in quantity), the transfer of data requires the presence of a Bluetooth-enabled computer. In spite of the fact that computers are now a commodity item, there are many populations (the elderly, the poor) who could benefit greatly from the use of medication tracking but who are unlikely to have a computer in the home. In these cases the MedTracker could be used to simply store the data and transfer could take place during a clinic visit.

In summary, the MedTracker provides an easy-to-use alternative to the MEMS cap currently used to assess adherence in many studies of drug and therapy efficacy, and adds some of the features available in more complex research solutions. We anticipate that the MedTracker will be a valuable tool for use in studies of treatment effects, as well as in our own studies of medication management in the elderly.