Timothy Peters-Strickland, Ainslie Hatch, Anke Adenwala, Katie Atkinson, Benjamin Bartfeld

The digital medicine system (DMS), a drug-device combination developed for patients with serious mental illness, integrates adherence measurement with pharmacologic treatment by embedding an ingestible sensor in a pill, allowing for information sharing among patients, health care providers (HCPs), and caregivers via a mobile interface. Studies conducted during the DMS development process aimed to minimize cognitive burden and use-related risks and demonstrated effective use of the technology. Human factors (HF) studies assessed the system's safe and effective use by the intended users for the intended uses. The patient interface was tested in six formative HF studies followed by a validation study. The HCP/caregiver interface was tested in one study before validation. All tasks critical to safety or necessary for effective use were included. Formative studies identified use-related risks and the causes of use problems to guide design modification. Validation of the patient and HCP/caregiver interfaces assessed risks of the final product. During the patient formative studies, design improvements were made to address problems and mitigate risks thought to be associated with a suboptimal system design or patient understanding of the system. In the validation study of the patient interface, 35 patients attempted 23 performance tasks, for a total of 805 attempts; 783/805 attempts were completed with success. One close call, 15 failures, and 6 difficulties occurred on these user tasks; only 3 of these were on a critical task. Residual risks resistant to mitigation were found to be of low severity based on the US Food and Drug Administration 2016 guidance. The final design of the DMS reflects input by the intended user populations through a comprehensive development methodology. In alignment with the US Food and Drug Administration goals for HF studies, the system was found to be safe and effective for the intended users, uses, and use environments.