Overconsumption detected by electronic drug monitoring requires subtle interpretation

Background: Electronic compliance monitoring has provided new variables to describe drug intake behavior and new strategies to improve compliance. How ever, as evaluated in this study, the recording of opening events of pill b ottles does not necessarily mean drug intake. Methods: In an open 3-week trial with an oral vitamin combination, drug int ake was recorded with use of an electronic pill box that contained 25 capsu les and that registered each opening of the bottle. Thirty-seven patients w ere asked to take one capsule every morning for 21 days, Opening and closin g events were related to the results of pill counts and patient. interviews at the end of the trial. Results: Drug consumption was 101.8% (663 recorded opening and closing even ts) in the 31 patients who completed the trial, Pill boxes were opened more than once by 10 patients on at least one monitored day. For seven patients the total number of opening mras >25 (range, 26 to 29) and thus exceeded t he number of capsules provided. A third interview of these patients reveale d real overconsumption in only two patients, Six patients remembered that t hey had shown the device to relatives or friends or that they had checked t o see whether they had closed the pill box well, thus turning a "curiosity event" into a drug intake event. Conclusion: In short-term studies particularly, such curiosity events may s ubstantially modify the electronic assessment of compliance surrogates, In these trials the combined evaluation of electronic openings, pill counts, a nd interviews may be a suitable way to reveal such opening without pill int ake.