Fantastic voyage: tracking adherence sensors in PrEP meds

Simon Collins, HIV i-Base

A recent study reported patterns in PrEP adherence by using meds that were made with tiny sensors inside. The sensors are harmless but provided a direct record of when people took PrEP.

Apart from the novelty of bringing Fantastic Voyage to HIV prevention, the study reported two important patterns.

One was that the days when PrEP was not taken were often clustered together, rather than just appearing to be random single days (p<0.003).

The second was that adherence and the clusters of missed days was associated with self-reported use of crystal meth [OR 5.0; CI 95: 2.2 to 11.5), p < 0.001].

The study included 71 HIV negative people using PrEP, with 63/71 continuing for at least 28 days. Mean age was 37 years (range: 18 to 69), 90% male, 77% white, 34% Hispanic. Most had stable housing (96%) housed and 75% were in paid work.

The 63 remaining participants provided just under 5000 observation days: average of 79 days (range: 29 to 105). Overall adherence was 86% but this steading declined over time (by about 90% each week, p<0.001).

An important caution that was not included discussing whether the missing days were part of a structured decision related to meth use. For example that adherence might have been good during the times when meth use increased risk of HIV – and conversely, when not using meth, PrEP might also not be needed.


Browne SH et al. Medication adherence patterns in persons prescribed ingestible sensor-enabled oral pre-exposure prophylaxis to prevent HIV infection. Clinical Infectious Diseases, ciac280, doi: 10.1093/cid/ciac280. (23 May 2022).

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