Overview
Error, Harm, and the Last Barrier
A medication error is a preventable event that may cause or lead to inappropriate medication use or patient harm.
A medication error is a preventable event that may cause or lead to inappropriate medication use or patient harm. An adverse drug event is the harm a patient actually experiences from medication exposure. These terms overlap, but they are not interchangeable. A dose caught before it is given is a medication error or near miss, not an adverse drug event. A patient who develops an expected adverse effect despite receiving the correct medication correctly has an adverse drug event, but not necessarily a medication error. This distinction matters because near misses expose weak points in the system before a patient is injured. Medication-use failures can begin when a drug is ordered, transcribed, dispensed, or administered. The practical nurse is often the last person able to interrupt the chain. Once the medication enters the patient, there may be no remaining barrier between an earlier error and clinical harm. Prevention therefore cannot depend on “being careful.” Fatigue, interruptions, similar packaging, incomplete information, and flawed electronic systems affect careful clinicians too. Safe practice builds several independent barriers so that one missed detail does...