Anti diuretic

Introduction

An Anti diuretic is a substance that helps to control fluid balance in an human’s body by reducing urination or opposing diuresis.

Its effects are opposite that of a diuretic.

Anti Diuretic Drugs :-

1. Antidiuretic hormone (ADH, Vasopressin), Desmopressin, Lypressin, Terlipressin
2. Thiazide diuretics, Amiloride.
3. Miscellaneous: Indomethacin, Chlorpropamide, Carbamazepine.

1. ANTI DIURETIC HORMONE

(Argenine Vasopressin-AVP)

Antidiuretic hormone (ADH) is a hormone that helps your kidneys manage the amount of water in your body.

The ADH test measures how much ADH is in your blood. This test is often combined with other tests to find out what is causing too much or too little of this hormone to be present in the blood.

About ADH hormone=

ADH is also called Arginine vasopressin. It is a hormone made by the Hypothalamus in the brain and stored in the posterior pituitary gland. It tells your kidneys how much water to conserve.

ADH constantly regulates and balances the amount of water in your blood.

Pharmacokinetics=

AVP is inactive orally because it is destroyed by trypsin. It can be administered by any parenteral route or by intranasal application.

The peptide chain of AVP is rapidly cleaved enzymatically in many organs, especially in liver and kidney.

Vasopressin Analogues=

• Lypressin– It is 8-lysine vasopressin. Though somewhat less potent than AVP and has longer duration of action (4-6 hours).

• Terlipressin- This synthetic pro-drug of vasopressin is specifically used for bleeding esophageal varices; may produce less severe adverse effects than lypressin.

• Desmopressin– This synthetic peptide, 12 times more potent antidiuretic than AVP, but has negligible vasoconstrictor activity.

Uses=

1. Diabetes insipidus :- DI of pituitary origin (neurogenic) is the most important indication for vasopressin. It is ineffective in renal (nephrogenic) DI, since kidney is unresponsive to ADH.

Drugs like -Aqueous vasopressin or lypressin injection is impracticable for long-term treatment.

Desmopressin 2 µg i.m. is the preparation of choice now for the same purpose.

2. Bed wetting in children and nocturia in adults- Intranasal or oral desmopressin at bed time controls primary nocturia by reducing urine volume.
3. Renal concentration test 5-10 U i.m. of aqueous vasopressin or 2 ug of desmopressin causes maximum urinary concentration.

Common Side Effects=

1. Gas or stomach cramps.
2. Nausea and vomiting.
3. Dizziness.
4. Headache.
5. Excessive sweating..
6. Labored breathing caused by narrowing of the airway.
7. Increased tiredness, which may result from low blood sodium levels.

2. THIAZIDES DIURETICS :-

Diuretic thiazides paradoxically exert an antidiuretic effect in DI.

High ceiling diuretics are also effective but are less desirable because of their short action.

Thiazides reduce urine volume in both pituitary origin as well as renal DI. They are especially valuable for the latter in which AVP is ineffective.

• Hydrochlorothiazide– less effective than AVP, it is more convenient and cheap even for pituitary origin DI; may reduce polyuria to some extent.
• Amiloride is the drug of choice for lithium induced nephrogenic DI

3. MISCELLANEOUS

• Indomethacin has also been found to reduce urine flow.
• Chlorpropamide It is a long-acting sulfonylurea oral hypoglycaemic, found to reduce urine volume in DI of pituitary origin but not in renal DI.
• Carbamazepine It is an antiepileptic which reduces urine volume in DI of pituitary origin.