Medication Error Reporting Practice Test

A 62-year-old woman (72 kg) is receiving vancomycin intravenously for cellulitis. Current medications: vancomycin 1,250 mg every 12 hours. Labs: serum creatinine increased from 0.9 to 1.8 mg/dL over 4 days (reference 0.6–1.3). No vancomycin levels were ordered or documented during therapy. Allergy: none known. Which medication error needs to be reported?

A 56-year-old man (100 kg, 182 cm) is prescribed rivaroxaban 20 mg daily for deep vein thrombosis. Current medications: rivaroxaban 20 mg daily (new) and phenytoin 300 mg nightly. Labs: serum creatinine 1.0 mg/dL (reference 0.6–1.3), alanine aminotransferase 20 U/L (reference 7–56). Allergy: none known. The pharmacist does not evaluate for drug interactions and dispenses rivaroxaban. What is the most critical error in this scenario?