Nocturnal enuresis

A 6-year-old boy is brought to the pediatrician by his parents due to recent bedwetting. He was toilet-trained at the age of 3 and has been able to stay dry during the day. However, he continues to have nighttime “accidents” 3-4 times per week. The patient consumes fluids in the morning and afternoon, but not prior to bed. The family recently moved from their home in the city to a suburban neighborhood, and he has experienced difficulty making new friends at school. Temperature is 37.2°C (99.0°F), blood pressure is 107/68 mmHg, and pulse is 79/min. A complete physical examination is noncontributory. The patient is subsequently trialed on scheduled timed voids overnight and a bedwetting alarm, both of which fail to control his symptoms. The patient is subsequently initiated on a medication that acts as an antidiuretic hormone analog. Which of the following medications was most likely prescribed?