Digital pill tracks HIV PrEP adherence with 98% accuracy

A digital pill that records when it is taken has been shown to be highly effective at helping patients adhere to pre-exposure prophylaxis (PrEP) treatment used to protect them from contracting HIV.

A pilot study, which involved 16 men who have sex with men (MSM) and a history of substance use, found that the system was 98% effective at tracking adherence to a once-daily oral PrEP regimen.

Each dose of PrEP was enclosed in the gelatin capsule with a radiofrequency transmitter. When swallowed, stomach acid dissolved the gel coating of the pill and activated the transmitter, which sent a signal that could be detected with a device worn on the body.

That created a digital record of when they took pills over a 90-day period, which could be shared via a smartphone app with their doctors.

The findings were cross-referenced by counting the number of pills returned at the end of the study and by analysing blood samples that measured the concentration of tenofovir, an ingredient in PrEP.

The DigiPrEP trial was funded by Gilead Sciences, which sells Truvada (emtricitabine/tenofovir disoproxil), the drug used in the study.

As well as helping the doctors monitor compliance with the treatment, the system also proved valuable to the PrEP users, who said having a record of when pills were taken gave them "piece of mind."

They also said the system could be improved by the introduction of reminders as well as "intervention systems which would help them take PrEP in the setting of their own barriers to adherence," such as substance use behaviour.

"Digital pills are not scary," said Peter Chai of Brigham and Women's Hospital in the US, who is the corresponding author for the study published in the Journal of Acquired Immune Deficiency Syndromes.

"They're novel devices being used clinically to measure drug adherence," he added, although he acknowledged that they are likely too expensive to be used at scale.

"While this technology will likely not be used in cheaper medications or those with less impact, it could improve outcomes for expensive or live-saving medications, like those for congestive heart failure, hepatitis C, or diabetes," said Chai.

With mass production, the price could be reduced to "fractions of a cent", he suggested.

One complaint about the platform from some subjects in the trial was that the reader was fairly bulky, and the team now say they will look into miniaturising it into a wristband format. Others said however that having to wear it was a reminder to take their PrEP.