PURPOSERecent innovations allow the integration of microelectronics into drug packaging, providing a continuous record of the interactions of the patient with the drug package. We hypothesized that adherence to oral tamoxifen, as measured by a pressure-activated microelectronic monitoring device, would be significantly discrepant from traditional measures of patient adherence, ie, patient self-report (SR) and pill counts (PCs).PATIENTS AND METHODSTwenty-six patients receiving oral tamoxifen therapy were assessed by patient SR, PCs, and Medication Event Monitoring System (MEMS; Aprex Corp, Fremont, CA) microelectronic monitoring. A microprocessor in the MEMS cap recorded each opening as a presumptive dose, listing the date, time, and duration of opening for later retrieval on a microcomputer. Patients were not informed that their adherence was to be monitored electronically or that PCs would be performed.RESULTSA total of 2,102 days (70.1 months) of tamoxifen therapy were monitored; patients were monitored...