Which of the following is the most common type of medication error?

Wrong patient
Wrong drug
Wrong duration
Underdosage

Wrong drug

Rationale: Of these answer choices, the "wrong drug" is the most common type of medication error, causing 16% of all errors. However, the actual most common type of medication error, which was not an answer choice, is giving an improper dose. This accounts for 41% of fatal medication errors.