• In medication safety terminology used across pharmacy technician study materials and safety taxonomies, an adverse event (specifically, a preventable adverse drug event) occurs when a medication error reaches the patient and results in harm or has the clear potential for harm (e.g., incorrect patient’s medication taken for several doses).

• By contrast, near misses (or “close calls”) are errors that are intercepted before they reach the patient, such as when a pharmacist catches incorrect directions during counseling (Option A), when a technician detects that a prescription was bagged but not yet verified (Option C), or when a technician finds a prescription placed in the wrong will-call bin before pickup (Option D). These represent process breakdowns with potential for harm but no patient exposure once intercepted.

• Therefore, the scenario most likely to lead to an adverse event is Option B, where the patient has already ingested medication intended for another patient. That constitutes an error that reached the patient, with a meaningful risk of harm, aligning with definitions for preventable adverse drug events.

References (Pharmacy Technician documents/Study Guides):

• NCC MERP (National Coordinating Council for Medication Error Reporting and Prevention) Taxonomy and definitions on medication errors, near misses, and events reaching the patient.

• ISMP (Institute for Safe Medication Practices) medication safety terminology and event classification used in community and institutional pharmacy practice.

• PTCB/ExCPT-aligned Pharmacy Technician Certification study guides: sections on medication safety, event reporting, and error prevention (definitions of “adverse event,” “medication error,” and “near miss/close call”).

• ASHP guidelines on preventing medication errors in community pharmacy workflows (verification steps, counseling interception points, and will-call bin best practices).