DIURETICS AND ANTI-DIURETICS
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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.
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.
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 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.
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.
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.
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.
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
In medicine, diuretics are used to treat heart failure,
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.
An antidiuretic is an agent or drug that, administered to an organism, helps control body water balance by reducing urination, opposing diuresis.
Antidiuretics(4) are the drugs that reduce urine volume, particularly in diabetes insipidus (DI) which is their primary indication.
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
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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