How do vasopressin receptor antagonists work?
Vasopressin antagonists are drugs that bind to vasopressin receptors (V1A, V1B and V2) and block the action of vasopressin (antidiuretic hormone, ADH), which is a hormone released by the pituitary gland. Vasopressin causes vasoconstriction and increases reabsorption of water by the kidneys.
What is the mechanism of action of tolvaptan?
Mechanism of action and uses Tolvaptan is a competitive antagonist at vasopressin V2 receptors. Its major action is in the renal collecting ducts to reduce water reabsorption and produce aquaresis without sodium loss, thus increasing free water clearance and correcting dilutional hyponatraemia.
Is vasopressin a Vaptan?
Arginine vasopressin (AVP) plays an important role in water and sodium homeostasis. It acts via three receptor subtypes—V1a, V1b, and V2—distributed widely throughout the body. Vaptans are nonpeptide vasopressin receptor antagonists (VRA).
How does ADH cause antagonist hyponatremia?
In some cases hyponatremia results from a defect in Na+/Cl- transport out of the impermeable thick ascending loop of Henle and distal convoluted tubule. In majority of cases hyponatremia results from continuous stimulation and secretion of vasopressin by non osmotic stimuli despite presence of serum hypoosmolality.
Where do Vaptans act?
Vaptans. The “vaptan” drugs act by directly blocking the action of vasopressin at its receptors (V1A, V1B and V2).
Why do Vaptans cause hypernatremia?
Moreover, hypokalemia reduces urine concentration and induces an increase in urine volume, thus resulting in hypernatremia in addition to the effect of tolvaptan.
What receptors does vasopressin work?
Vasopressin acts on V1, V2, V3, and oxytocin-type receptors (OTR). V1 receptors are found on vascular smooth muscle of the systemic, splanchnic, renal, and coronary circulations.
What is the function of anti diuretic hormone?
Antidiuretic hormone (ADH) is a chemical produced in the brain that causes the kidneys to release less water, decreasing the amount of urine produced. A high ADH level causes the body to produce less urine. A low level results in greater urine production.
What is the difference between vasopressin and desmopressin?
Desmopressin (1-deamino-8-O-arginine-vasopressin, DDAVP) is a synthetic analogue of arginine vasopressin. It has 10 times the antidiuretic action of vasopressin, but 1500 times less vasoconstrictor action. These modifications make metabolism slower (half-life of 158 min).
What is tolvaptan used for?
Tolvaptan is used to treat hyponatremia (low sodium in the blood) in patients with heart failure or syndrome of inappropriate antidiuretic hormone (SIADH).