A 30-yeаr-оld mаn presents tо yоur clinic complаining of excessive thirst and frequent urination for the past few months. Urine testing reveals a low urine osmolarity, which fails to increase after subjecting the patient to a water deprivation test and injection of desmopressin. Further into the encounter, the patient reveals that he has been on a mood stabilizer for bipolar disorder for several years. Which of the following is the most likely cause of his polyuria?