DIURETICS AND ANTI-DIURETICS

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DIURETICS AND ANTI-DIURETICS

hi friends i am here with my blog titled as "DIURETICS AND ANTI-DIURETICS"

definition:

A diuretic is a drug which elevates the rate of urination and hence provides means for forced diuresis. There are many categories of diuretics. (1)All types of diuretics increase the excretion of water from the bodies, although each class does so in a separate way.

Types

High ceiling loop diuretics:
High ceiling diuretics are those diuretics that may cause substantial diuresis - i.,e up to 20% of the load of NaCl and water that is filtered..(1) This is large when compared to the normal renal sodium reabsorption that leaves only 0.4% of filtered sodium in urine.
Loop diuretics are the diuretics that have this ability, and often synonymous with high ceiling diuretics. Loop diuretics, such as furosemide reduce the ability of the body to reabsorb sodium at the ascending loop part of the nephron which leads to water retention in urine as water normally follow sodium back into extracellular fluid (ECF). Some of the examples of high ceiling loop diuretics include torsemide, ethacrynic acid, and bumetanide.

Thiazides
Thiazide-type diuretics are the diuretics like hydrochlorothiazide and they act on the distal convoluted tubule part of the nephron and inhibit the sodium-chloride symport that leads to a retention of water in urine, as water normally follows penetrating solutes. Frequent urination occurs due to elevated loss of water that has not been retained from the body as a result of a relationship with sodium loss(2) from the convoluted tubule of nephron. the long-term effect is due to an unknown vasodilator effect that decreases blood pressure.

Carbonic Anhydrase Inhibitors
Carbonic anhydrase inhibitors inhibit the enzyme named carbonic anhydrase which is seen in the proximal convoluted tubule part of the nephron. This results in the several effects including bicarbonate retention, potassium retention in urine and decreased absorption of sodium. Drugs of this class include acetazolamide and methazolamide.

Digitalis
Digitalis increases the urine output by increasing the cardiac output and increasing the circulation through kidneys. Digitalis has diuretic effect on the heart failure patients due to cardiac edema.
Potassium-sparing diuretics
These are the diuretics that do not promote secretion of potassium in the urine; thus, potassium is spared and not lost as much like in other diuretics. The term "potassium-sparing" refers to an effect rather than a mechanism, the term almost always refers to two specific classes that have their effect at similar locations.

Aldosterone antagonists
spironolactone, is a competitive antagonist of aldosterone. Aldosterone normally elevates sodium channels in the principal cells of the collecting duct of the nephron and late distal tubule part of the nephron. Spironolactone prevents aldosterone from entering into the principal cells, preventing Na reabsorption.
Epithelial sodium channel blockers: amiloride and triamterene come under this category.

Calcium-sparing diuretics
The term "calcium-sparing diuretic" is used to identify the agents that result in a relatively low rate of excretion of calcium in the body
The reduced concentration of calcium in urine can lead to an increased rate of calcium in serum. The sparing effect on calcium(7) can be beneficial in hypocalcemia, thiazides and potassium-sparing diuretics are considered to be calcium-sparing diuretics. These potassium-sparing diuretics leads to a net increase in the calcium lost in the urine, but the increase is smaller than the increase associated with other diuretic classes.

Osmotic diuretics
Compounds such as mannitol are filtered in the glomerulus part of the nephron, but cannot be reabsorbed. Their presence leads to increase in the osmolarity of filtrate. To maintain the osmotic balance, water is retained in urine.

Low ceiling diuretics
The term "low ceiling diuretic" is used to indicate that diuretic has a rapidly flattening dose effect .It refers to a pharmacological profile. However, there are certain classes of diuretic which usually fall into this category, such as the thiazide

Uses
In medicine, diuretics are used to treat heart failure,
liver cirrhosis,
hypertension and
certain kidney diseases.

* Some diuretics, such as acetazolamide, help to make the urine more alkaline(4) and are helpful in increasing excretion of substances such as aspirin in cases of overdose or poisoning.
* Diuretics are often abused by sufferers of eating disorders, especially bulimics, in attempts at weight loss.

*

That is, the reduction in blood pressure is not due to decreased blood volume resulting from increased urine production, but occurs through other mechanisms and at lower doses than that required to produce diuresis.
* Indapamide was specifically designed with this in mind, and has a larger therapeutic window for hypertension (without pronounced diuresis) than most other diuretics.
increased urination

AntidiureticS
An antidiuretic is an agent or drug that, administered to an organism, helps control body water balance by reducing urination, opposing diuresis.

Uses
Antidiuretics(4) are the drugs that reduce urine volume, particularly in diabetes insipidus (DI) which is their primary indication.

Examples
These are classified as:

Antidiuretic hormones: ADH/Vasopressin: A hormone secreted by the posterior lobe of the pituitary gland that constricts blood vessels, raises blood pressure, and reduces excretion of urine. Also called antidiuretic hormone.

, Desmopressin"; Desmopressin(5) (trade names: DDAVP, Stimate, Minirin) is a synthetic replacement for the hormone vasopressin, the hormone which reduces the urine production. It may be taken nasallyiv form or as a tablet. Doctors usually prescribe Desmopressin(7) most frequently forthe treatment of diabetes insipidus(7) or nocturnal enuresis
, Lypressin, Terlipressin
Chlorpropamide, Carbamazepine

REFERENCES:

1.http://en.wikipedia.org/wiki/Diuretic(ACCESSED ON 28/4/11,5 P.M)
2.http://www.icm.tn.gov.in/drug%20formulary/DIURETICS(14).htm(ACCESSED ON 28/4/11,5 P.M)

3.http://en.wikipedia.org/wiki/Antidiuretic(ACCESSED ON 28/4/11,5 P.M)

4.http://www.medterms.com/script/main/art.asp?articlekey=7103(ACCESSED ON 28/4/11,5 P.M)
(ACCESSED ON 28/4/11,5 P.M)

5.http://en.wikipedia.org/wiki/Desmopressin(ACCESSED ON 28/4/11,5 P.M)

6.http://www.bookrags.com/research/diuretics-and-antidiuretic-hormones-wap/(ACCESSED ON 28/4/11,5 P.M)

7.Rang and Dales Pharmacology by Rang, Dale, ritter, moore, churchill livingstone publishers, 6th edition pageno:(375-384)

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Comments

Gangadhar Hari's picture

Nice explanation Sandhya. I think there are some more important clinical uses of diuretics. I have a query for you.. What are potassium wasting diuretics?? How they cause it??
Sandhya Sravya malla's picture

the diuretics that promote excretion of potassium are called as potassium wasting diuretics and some of the examples of these type include furosemide,thiazides like hydrochlorthiazide etc..... pharma warriors.....
Bhavani Prasad.V's picture

Nice write up Sravya. Well my query is - Can you explain the mechanism of action of Aldosterone antagonists in detail, like they are also called Potassium sparing diuretics right? So can you explain about it?

Regards,

Bhavani Prasad.V

Sandhya Sravya malla's picture

thank you and coming to your query potassium sparing diuretics are otherwise called as aldosterone antagonists due to their similar chemical(steroidal) structure and these so called potassium sparing diuretics compete with aldosterone antagonists by blocking Na channel receptors. mechanism of action: Spironolactone and triamterene are two of the examples that comes under potassium sparing diuretics. Aldosterone is a hormone that is released during stress conditions and causes an elevation in potassium excretion and a declines excretion of sodium as well as water. Since drugs from this family acts antagonistically to the effects of this hormone aldosterone then potassium is spared in body, and sodium and water are excreted out. Aldosterone antagonists are nothing but the receptor antagonists that act at the mineralocorticoid receptors. Antagonism of these receptors reduces the sodium reabsorption in the collecting duct part of the nephron in the kidneys. This action interferes with sodium/potassium exchange, reducing the urinary potassium excretion and increasing water excretion (diuresis). In congestive heart failure disease, they are used in along with other drugs for additive diuretic effect, which decreases edema and cardiac workload.

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