Earlier this week, the FDA granted its first-ever approval for a “smart pill”–a psychiatric medication that comes with a tiny sensor in every dose. The system is called Abilify MyCite. The idea is that when you take the pill, the sensor sends a signal to a patch you wear on your stomach indicating that you’ve correctly dosed. The patch then transmits the information to a smartphone app that logs and tracks your medication schedule, as well as other relevant metrics like mood changes.
Most of the media coverage in the immediate wake of the FDA announcement fretted–quite understandably–about the possibility that this technology could enable or encourage “big brother”-style monitoring of an individual’s personal mental health. The tracking app can be accessed by the prescribing doctor plus four other people, such as family members (if the patient grants consent), and it’s intended to help solve the problem of patients simply forgetting to take their meds. That sounds benign. But would a patient feel pressure to take this “digital medicine” in the first place, knowing there’s a digital audience watching?
All good food for bioethicist thought. But we wondered about something more practical: How on earth do you quality-test the product design for a piece of ingestible technology?
“Testing the ingestible with real human subjects was completely out of scope,” says Manish Mathuria, CTO and founder at Infostretch, the company that participated in testing the patch. (Infostretch worked on this 10 years ago, before it received FDA-approval.) The pill’s technology works in a clever way: Once the electrolytes in stomach fluids touch the sensor, they act as conductive “battery acid,” turning the sensor into a battery with enough juice (zing!) to temporarily transmit a signal that the patch can sense.
Successfully transmitting a signal through the stuff inside you is a tremendous challenge. There’s really only one solution, if you think about it. Proteus Digital Health (which invented the pill, sensor, and patch) “had to create a humanoid in a lab and simulate real-life conditions to test the ingestible,” says Mathuria. We weren’t able to get a picture of the “humanoid,” but Lyford says it looks basically the same as a CPR dummy: “a face, a mouth, and, most importantly, a stomach located the right distance from where the patch would be.”
This dummy-with-a-fake stomach was crucial to defining how much battery power was necessary to get a usable signal from the pill to the patch. “There’ s this continual tension about how much power to use. How big a battery do you really need in the pill? Are there certain frequencies that go through liquid and tissue better?” Lyford explains. A lower-strength signal will use less battery power and last longer, but a higher-strength signal will be easier to detect by the patch, and also give more latitude for where it can be placed. “You want to be able to say that this is the distance the pill is from the sensor, and this is the minimum power it needs,” says Lyford. “If you were in the [testing] room, you’d see a person opening the dummy, putting the sensor in the stomach area, closing it up, and applying the patch.”
In this case, testing showed that the patch needs to be placed in a very specific place, close to where the pill ends up in the stomach: on the left side of the rib cage. “One of the challenges of medical tech is that by definition your user isn’t going to be at 100% when they’re using it, so you have to make allowances and test for that,” Lyford adds. “To get FDA approval, the way the patient is likely to actually use the product matters. Sometimes the product is going to be finicky and that’s going to just have to be a condition of use that we make really clear in the instructions. In this case, the patch can’t be on the leg and still work.” (When used as directed, the device has a 98% success rate.)
This kind of gross-anatomical validation of ingestible technology provides a performance envelope for certain components that can be translated into digital simulations for further testing. But as smart pills keep evolving, “we’ll probably need to break out the dummy again,” says Lyford.
Oh and if you’re wondering what happens to the ingestible sensor after its work is done: you’re gross. But so are we! So we asked. Turns out that the “smart” part of the pill is smaller than a grain of sand—Proteus claims that it’s the world’s smallest medical device—so “it gets ‘evacuated’ safely and unnoticeably,” Lyford says. “That’s another challenge with this technology: dancing around how to talk about these issues.”