BETHESDA, MD 11 Feb 2016—By having a log of when oral antihypertensive drug doses reach a patient's stomach, healthcare providers at one health system have one more piece of evidence to consider when investigating why blood pressure readings remain higher than desired.
Barton Health Family Medicine Clinic in South Lake Tahoe, California, has been using Proteus Digital Health, Inc.'s feedback system for select patients since December, said internist and pediatrician Allison Steinmetz.
This use, according to Barton Health and Proteus, marks the first implementation of the feedback system in the United States aside from clinical trials.
"The patients that we're basically looking for are people who have borderline-controlled or out-of-control high blood pressure," Steinmetz said. "They also need to be patients that would be able to use [a tablet computer]. . . . They don't have to be tech-savvy at all."
Proteus Discover, as the feedback system is now known, consists of an ingestible sensor, a wearable sensor, and a software application.
The system's predecessor entered the market as a means for "unattended data collection for clinical and research applications," according to an FDA database on medical devices.
In June 2015, the system became an aid in measuring medication adherence in instances when the 6.5 x 2 mm ingestible sensor is consumed along with medication.
How it works. The ingestible sensor "communicates a unique and private digital code" upon contact with stomach fluid, according to a 2015 engineering journal article by former and current company personnel.
In brief, once in contact with the stomach's electrolytic fluid, the ingestible sensor's magnesium and cuprous chloride layers become the anode and cathode, respectively, of a battery. This battery provides the energy for the sensor's chip to send data to a receiver—the wearable sensor—for four minutes, on average.
The company said the coin cell–powered, water-resistant wearable sensor with 4 or 16 Mb of memory can collect such information as heart rate, activity, body angle, and skin temperature in addition to the time-stamped events communicated by the ingestible sensor.
As for the software application, the journal authors described it as a mobile device–based user interface.
Researchers reported in the American Journal of Managed Care in 2011 that the feedback system correctly detected patients' and healthy persons' consumption of the ingestible sensor 96.7% of the time, on average. Among these 111 study participants, the adverse event most commonly related to the feedback system was a mild skin rash from the wearable sensor's adhesive electrodes.
Potential. Research underway, according to ClinicalTrials.gov, includes a study of the feedback system as an alternative to directly observed therapy for the treatment of tuberculosis.
And a new drug application for an Abilify (aripiprazole) tablet containing the ingestible sensor is under review by FDA, according to Otsuka Pharmaceutical Co. Ltd. and Proteus Digital Health.
Brent I. Fox, a pharmacy and healthcare informatics researcher at Auburn University in Alabama, said the feedback system holds the potential to be "a great leap forward" in the measurement of adherence.
"We've tried various methods over the years to improve adherence—reminders, those kinds of things," Fox said. "We've tried better methods to measure adherence—self-report all the way to MEMSCaps and similar tools."
A MEMSCap (WestRock Healthcare, Richmond, VA) records the event of someone opening the medication container, which may not necessarily mean the patient ingested a dose, he said.
"Adherence is really hard to manage," Fox said, but "measuring [it] is harder."
The potential for Proteus Discover to greatly advance medication therapy by tying an accurate adherence measure to real-time clinical measures, such as blood pressure and blood glucose concentration, is an exciting possibility for the future, he said.
Another future possibility he mentioned is that the system, through a portal, could one day enable adult children to monitor their parents' medication adherence from afar.
Downsides to the feedback system include the likely additional cost of including an ingestible sensor with each tablet or capsule, Fox said.
However, he said, payers may be interested in covering the cost for having "a better measure of adherence." Payers could then target for intervention the patients whose chronic conditions, if not better controlled, will need costlier intervention, such as hospitalization.
Fox pointed out a possibly larger but not insurmountable barrier: concerns among patients about ingesting a device that records their activity.
"I don't doubt that there are patient populations that think [the device] is pretty cool," he said, but some will not.
In practice. Although Barton Health is still recruiting patients for its pilot project with the feedback system, Steinmetz said, she has already used its data to adjust patients' antihypertensive drug regimens.
"One thing that I've seen is it helps with the timing of the medication," she said.
The drug-taking logs for some patients showed that they regularly took their morning dose of antihypertensive medication but did not do as well with their afternoon dose, Steinmetz explained.
To solve this adherence problem, she said, the healthcare providers opt for a medication or formulation that needs to be taken only once a day.
The drug-taking logs have also provided heretofore missing information as a healthcare provider contemplates what to do when blood pressure readings suggest an inadequate regimen.
Now, before increasing a medication's dosage, she said, the provider knows whether a patient's blood pressure readings reflect all the prescribed doses of the antihypertensive regimen.
Steinmetz said the pilot project involves only antihypertensive medications—calcium channel blockers, angiotensin-converting enzyme inhibitors, angiotensin II receptor blockers, diuretics, and beta-blockers—available as generic products. Eligible patients have a treated blood pressure greater than 140/90 mm Hg and are already using the project's medications.
To date, she said in mid-January, patients using the feedback system have been in their 50s to 90 years old.
The patients have insurance other than Medicare and do not incur additional cost for using the feedback system, said Molly Hucklebridge Coolidge, a communications specialist for Barton Health.
All their antihypertensive doses are supplied as capsules, she said. A compounding pharmacy encapsulates each tablet or capsule with an ingestible sensor.
Coolidge said the health system is considering adding its cardiology service to the project.