Desmopressin is a synthetic analogue of vasopressin (antidiuretic hormone) that primarily acts on V2 receptors in the kidneys to promote water reabsorption, thereby reducing urine output. It is clinically significant for managing conditions such as diabetes insipidus and nocturnal enuresis, as it helps to concentrate urine and improve fluid balance. A key consideration is its potential to cause water retention, leading to hyponatraemia, particularly in susceptible patients.