Antidiuretic hormone or vasopressin is a peptide hormone discharged by the posterior pituitary gland in response to rising plasma tonicity or falling blood pressure.Vasopressin posses antidiuretic and vasopressor properties.A deficiency of this hormone leads to diabetic insipidus.
Vasopressin is a polypeptide hormone with 9 amino acids.It acts on three forms of receptors within the Body.
1.V1a- On blood vessels
2. V1b-Increase the discharge of ACTH by pituitary
3. V2-On renal Tubules.
Stimulation of V1a- receptor causes constriction of blood vessels, whereas stimulation of V1b -receptor causes increase in the release of ACTH by the pituitary.stimulation of V2 receptor causes increased reabsorption of water from the renal tubules.V1a receptor stimulation can cause activation of phospholipase C and formation of inositol triphosphate, that produce increase concentration of Ca within the cell.V1a selective peptide has been synthesized in the form of Vasotocin, that causes constriction of blood vessels.An oral nonpeptide V1a receptor antagonist is additionally available, that is known as relcovaptan.Such antagonist of V1a could have useful effects in cases of high blood pressure and cardiac failure.Conivaptan act as an antagonist at each V1a and V2 receptors.it is being employed for the treatment of hypernatremia.Some extrarenal V2 -like receptors causes the discharge of coagulation factors VIIIc and von Willebrand factor.Vasopressin secretion is raised by the increase in the osmotic pressure and by alcohol.At large doses it will cause contraction of all smooth muscle, raising the blood pressure and causing intestinal colic.This stimulation of smooth muscle by antidiuretic hormone produces tachyphylaxis.Construction of coronary arteries could cause angina pectoris, myocardial infarction or death.Desmopressin may be a long-acting synthetic analog of antidiuretic hormone.It has negligible activity on the V1 receptors and therefore doesn’t cause vasoconstriction in the therapeutic doses.also, it has an extended duration of action as compared to vasopressin and therefore is used once or twice daily.it causes a significant antidiuretic impact.
Uses:
1. Pituitary diabetes insipidus: in this disease, because of deficiency of vasopressin (Antidiuretic hormone), Thre is the increased production of pee because of the inhibition of water reabsorption from the distal renal tubules.Desmopressin is used orally, intranasally, Intravenously, and subcutaneously. 10-40mcg is used intranasally daily in one to 3 divided doses.Each nasal spray delivers 10mcg of desmopressin .1-4mcg of desmopressin is used by subcutaneous or intramuscular injection every 12-24 hours.Aqueous antidiuretic hormone acts just for 3 to 6 hours, so it’s not usually used for the treatment of diabetes insipidus.
2. Nocturnal enuresis (Abnormal discharge of urine at nighttime during sleep): 0.1-0.2 of an intranasal spray of desmopressin is used for nocturnal enuresis.
3. Bleeding from esophageal varices: Liquid vasopressin is used for the treatment of hemorrhage from esophageal varices in a very dose of 0.1-0.5 units/minute by IV infusion.its stops the bleeding by causing constriction of blood vessels.Terlipressin ( A prodrug of vasopressin) is currently usually used a drug for this purpose.Terlipressin is converted in the body into lysin vasopressin and act for 4 hours for 2-3 days.Desmopressin isn’t effective in such cases, because of its weak impact on blood vessels.
4. Hemorrhagic Disease: Desmopressin and vasopressin are utilized in the treatment of hemophilia A} and Von Willebrand’s disease, as each of those medicines will cause the release of factor VIIIc and von Willebrand factor.
5.With local Anesthetics: Felypressin may be a derivative of vasopressin and may be used in combination with local anesthetics to prolong their impact on local anesthesia by causing constriction of their local blood vessels.It is utilized in those cases in which epinephrin and different alpha agonist are contraindicated.
Adverse Effects:
Adverse effects associated with the use of antidiuretic hormone are Nausea vomiting, Vertigo, Fluid Retention, sweating, abdominal cramps, Tremors, the desire to defaecate, angina attack or MI as a result of the constriction of coronary arteries, hypersensitivity reaction, peripheral ischemia and rarely gangrene.
Contraindications:
This drug is contraindicated in vascular illness particularly disease of coronary arteries and chronic nephritis. Use with cautions in Hypertension(High Blood Pressure) heart failure, migraine, epilepsy, asthma and different condition which could be aggravated by water retention.
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