How often should investigators check that each subject is following the instructions for using the investigational product?

• A. At intervals appropriate for the trial.
• B. Daily.
• C. Weekly only.
• D. Never.

Answer: (A)

Ensuring that subjects follow the investigational product’s instructions is an ongoing responsibility of the investigator, tied to both subject safety and data integrity. The frequency of checking adherence isn’t a one-size-fits-all rule; it should be determined by the trial’s protocol and monitoring plan, taking into account how complex the dosing is, how often the product is used, its safety profile, and how often subjects come in for visits. Checking adherence at intervals appropriate for the trial allows timely detection of noncompliance, enables retraining or clarifications as needed, and ensures that the exposure data and safety assessments are accurate. Fixed daily or weekly checks aren’t universally required and can be impractical, while never monitoring would jeopardize participant protection and data quality.