The latest weapon in the fight against opioid addiction may be sensors in prescription opioids that alert physicians whenever their patients pop a pill. These digital pills aren’t on the market yet, but a small test run shows that they can help doctors monitor how patients use prescription painkillers at home.

By prescribing opioids equipped with radio transmitters to patients treated for broken bones, researchers tracked patients’ pill use in real time. The research team, led by Peter Chai at Harvard Medical School’s Brigham and Women’s Hospital, found that most of the patients started spacing out their doses after a few days, and stopped before their pills ran out, according to the study published in the journal Anesthesia and Analgesia. (The participants turned their remaining pills in to their docs).

Prescribing too many pills might lead patients to take more than they need, the study says — or leave them with extra pills to be sold. So giving researchers a way to track how many pills patients actually use could help doctors write better opioid prescriptions that leave fewer pills left over. Digital pills could also help doctors spot — and stop — dangerous drug use early. This level of detail is a first: typically, doctors have no way to monitor opioid use once a patient goes home with a bottle of pills. “We’re placing the onus of one of the most dangerous medicines we have into the hands of patients,” says Chai, a physician and medical toxicologist at Brigham and Women’s Hospital.  

Chai wanted to know if there was a way to spot problematic drug use as the behavior emerges. If someone suddenly starts taking their prescribed painkillers more frequently, for example, it could mean they’re suffering from a painful complication. Or it could mean they’re growing tolerant to the drug, and could begin misusing it. “Those are two different conversations,” Chai says — and they’re ones that are only possible if a doctor can track their patients’ pill use.

That’s where the digital pills come in. Made by a Florida-based company called eTectRx, they’re gel capsules that contain both the drug and a radio transmitter “about the size of a sesame seed,” Chai says. (They’re a little different from the digital versions of antipsychotic Abilify, which the Food and Drug Administration just approved.)

Once the pill hits the patient’s stomach, the gel cap dissolves — releasing both the oxycodone tablet and the transmitter. The transmitter powers up when it touches stomach acid, and signals to an iPod-sized device via a patch stuck to the patient’s belly.  This device then beams a message to a database in the cloud, telling the doctor that the patient has swallowed a pill. (Patients need to put on the device when they take the pill in order for it to register.) Eventually, the patient poops out the tiny transmitter. Chai says he does not want the transmitters back.

The team sent 15 patients who’d been treated for broken bones home with 21 of these pills, along with instructions to take them for a week as needed. The researchers found that most patients started tapering their opioid doses on their own, and stopped after about four days — before the full week was up. None took all 21 pills, and most took many fewer — which means doctors might be sending people with fractures home with too many painkillers that could then be sold or misused.

The researchers also spotted an alarming trend: people were taking painkillers right before going to sleep to pre-empt waking up with pain. But Chai says this could lead to dangerous drops in breathing for some people — and it’s a practice they might not have identified without the digital pills.

It’s still early, but Chai says that the next round of studies will use an even more sophisticated version of these digital pill detectors. “We’re playing with the 1990s iPod. We have the iPhone X now,” Chai says. Of course, the patients will still actually have to wear the device — when they forgot, their doctors were left just as in the dark as before.