Desmopressin and Vasopressin Therapy

Arginine vasopressin (AVP), also called antidiuretic hormone, is synthesized in the hypothalamus and released from the posterior pituitary. Its effects depend on the receptor it reaches. At renal collecting-duct V2 receptors, AVP inserts aquaporin-2 water channels into the tubular membrane. Water moves back into the circulation, urine becomes concentrated, and serum sodium is protected from rising. At vascular V1a receptors, AVP causes vasoconstriction. This receptor difference explains why the two drugs have very different clinical roles: - Desmopressin is a synthetic AVP analogue designed to produce strong V2 antidiuretic activity with little V1 pressor effect. It retains free water and reduces urine volume. - Vasopressin has both V1a vasoconstrictor and V2 antidiuretic effects. In critical care, it is used primarily as a vasopressor. The newer terms arginine vasopressin deficiency (AVP-D) and arginine vasopressin resistance (AVP-R) replace central and nephrogenic diabetes insipidus, respectively. The terminology matters because these disorders are about water regulation, not insulin or glucose.