CNS Pharmacology USMLE Step 1 Practice Question

A 12-year-old boy is brought to his pediatrician by his mother, who reports that he has experienced easy bruising and recurrent nosebleeds since early childhood. She notes that minor cuts take unusually long to stop bleeding and that he bruised extensively after a dental extraction at age 8. His vital signs are within normal limits, and physical examination reveals several ecchymoses in various stages of healing on his extremities. Laboratory studies demonstrate a normal platelet count of 210,000/µL, a prolonged bleeding time of 12 minutes, normal PT and aPTT, and significantly reduced ristocetin cofactor activity consistent with von Willebrand disease. Before a scheduled minor surgical procedure, he is administered a drug intranasally that promotes release of von Willebrand factor and factor VIII from endothelial storage granules. Which of the following medications was most likely used?