F) Trace Sheet Monitors
Three companies sell devices, which determine when each dose of medication is removed from multiple cavities in a package by having an electrically conductive “trace” in a frangible cover over each cavity. When the medication is removed the trace is broken. By periodically passing electric current through the traces, it is possible to determine when medication is removed from each cavity. Figure 1 shows the general features of a trace sheet monitor.
You can obtain details regarding specific commercial devices by checking with the companies.
While these trace sheet monitors are attractive, they would pose significant problems if used to dispense anti-TB medications since one of the anti-TB medications used in the initial phases of therapy, ethambutol, is hygroscopic and needs to be protected against ambient moisture.
Moisture protection could be achieved by filling the cavities in the package with medication and sealing the cover over the cavities in a factory. However, since the dosage of medication ingested by the patient varies from 2 to 5 pills per day depending on the weight of the patient this would require four different packages of medication in the supply lines from the factory to the clinic. This would pose significant logistics problems.
To avoid these logistics problems the cavities could be filled in the clinic. However, it would be difficult to make sure that the cover was properly sealed to each cavity so as to prevent moisture from entering the cavities.
A second partial solution to the problem would be to supply the caregiver with small flexible water-proof packages each containing two or three pills of the multiple drug combination preparation that contains ethambutol that is used in the initial phase of therapy. The caregiver could use different combinations of these two packages to fill the cavities in the trace sheet monitor with 2, 3, 4, or 5 pills according to the weight of the patient.
For the continuation phase of therapy where ethambutol is not used and protection against moisture is probably not needed, the caregiver could place loose pills in the cavities of the trace sheet monitor without preliminary packaging.
In the future ethambutol maybe replaced with a drug that is not hygroscopic. If so, trace sheet monitors could be filled in the clinic with loose pills.
Trace Sheet Monitors are probably not optimal for TB medications at this time except in the continuation phase, but may become more practical in the future.
POTENTIAL AND EXISTING MEDICATION MONITOR DESIGNS
I. Cover and Cap Opening Monitors
II. Dose Removal Monitors