Potassium Carbonic anhydrase

Carbonic anhydrase is an enzyme that produces free hydrogen ions, which are then exchanged for sodium ions in the kidney tubules. Carbonic anhydrase inhibitors inhibit the action of the enzyme carbonic anhydrase This effect results in the excretion of sodium, potassium, bicarbonate, and water. Carbonic anhydrase inhibitors also decrease the production of aqueous humor in the eye, which in turn decreases intraocular pressure (IOP) (ie, the pressure within the eye). 

Thiazide and related diuretics, loop diuretics, potassium-sparing diuretics, carbonic anhydrase inhibitors, triamterene Avoid exposure to sunlight or ultraviolet light (sunlamps, tanning beds) because exposure may cause exaggerated sunburn (photosensitivity reaction). Wear sunscreen and protective clothing until tolerance is determined. 

Drugs of this group inhibit activity of carbonic anhydrase, an enzyme that catalyzes the reversible reaction of water and carbon dioxide, which forms carbonic acid. The mechanism of action of this group of drags is not fuUy understood. However, inhibition of carbonic anhydrase activity leads to a reduction of carbonic acid formation and an increase in bicarbonate, sodium, and potassium excretion with urine, which eventually leads to a significant increase in the process of excreting water from the organism. 

Acetazolamide is an aromatic sulfonamide used as a carbonic anhydrase inhibitor. It facilitates production of alkahne urine with an elevated biocarbonate, sodium, and potassium ion concentrations. By inhibiting carbonic anhydrase, the drug suppresses reabsorption of sodium ions in exchange for hydrogen ions, increases reflux of bicarbonate and sodium ions and reduces reflux of chloride ions. During this process, chloride ions are kept in the kidneys to cover of insufficiency of bicarbonate ions, and for keeping an ion balance. Electrolytic contents of fluid secreted by the kidneys in patients taking carbonic anhydrase inhibitors are characterized by elevated levels of sodium, potassium, and bicarbonate ions and a moderate increase in water level. Urine becomes basic, and the concentration of bicarbonate in the plasma is reduced. 

Mechanism of Action A carbonic anhydrase inhibitor that reduces formation of hydrogen and bicarbonate ions from carbon dioxide and water by inhibiting, in proximal renal tubule, the enzyme carbonic anhydrase, thereby promoting renal excretion of sodium, potassium, bicarbonate, and water. Ocular Reduces rate of aqueous humor formation, lowers intraocular pressure. Therapeutic Effect Produces anticonvulsant activity. 

Carbonic anhydrase inhibitors Loop diuretics Osmotic diuretics Potassium (K )-sparing diuretics... 

It does not inhibit carbonic anhydrase. Loss of potassium is less marked but chance of hypochloremic alkalosis are greater. It is an irritant and upon oral administration it produces diarrhoea, gastrointestinal bleeding may occur at higher dose. Chances of hearing loss are greater. So, due to their uniform toxicity, they are no longer used. 

Carbonic anhydrase influences the tubular reabsorption of sodium in proximal tubule where biocarbonate absorption occurs and in the distal tubule where sodium is exchanged for potassium or hydrogen ion and bicarbonate is formed as the accompanying anion. The hydration of carbon dioxide takes place under the influence of enzyme carbonic anhydrase which forms carbonic acid which dissociates and breaks into hydrogen and carbonate ions. 

Apical membrane Na+/H+ exchange (via NHE3) and bicarbonate reabsorption in the proximal convoluted tubule cell. Na+/K+ ATPase is present in the basolateral membrane to maintain intracellular sodium and potassium levels within the normal range. Because of rapid equilibration, concentrations of the solutes are approximately equal in the interstitial fluid and the blood. Carbonic anhydrase (CA) is found in other locations in addition to the brush border of the luminal membrane. 

It is about an active mechanism depending on the Na+-K+-ATPase enzyme located in the lateral plasma membrane of the endothelial cells. It enables the penetration of potassium into the cell against the excretion of sodium into the aqueous humor. Then this latter becomes hypertonic in comparison with the stroma and thus drains the water. In normal conditions, the pump can adapt to the physiological needs. Actually, the moves of the sodium ion are relative to those of the bicarbonate ion (responsible for the negative polarization of the back side of the endothelial cell) and to the pH variation. And yet, the bicarbonate comes from the aqueous humor and from the intracellular transformation of carbon dioxide and water by carbonic anhydrase. All of this shows the good functioning of the pumps depends on the integrity of the plasma... 

Diuretics work by increasing the amount of sodium and fluids excreted by the kidneys. Less fluid means less total blood volume and improved circulation and blood pressure. There are five main classes of the drug loop diuretics, thiazide diuretics, potassium-sparing diuretics, osmotic diuretics, and carbonic anhydrase inhibitors. 

Spironolactone competitively inhibits the physiologic effects of the adrenocortical hormone aldosterone on the distal tubules, thereby producing increased excretion of sodium chloride and water, and decreased excretion of potassium, ammonium, titratable acid, and phosphate. Spironolactone is a potassium-sparing diuretic that has diuretic activity only in the presence of aldosterone, and its effects are most pronounced in patients with aldosteronism. Spironolactone does not interfere with renal tubular transport mechanisms, and does not inhibit carbonic anhydrase. 

AMIODARONE CARBONIC ANHYDRASE ANTAGONISTS, LOOP DIURETICS, THIAZIDES Risk of arrhythmias Cardiac toxicity directly related to hypokalaemia Monitor potassium levels eveiy 4-6 weeks until stable, then at least annually... 

MEXILETINE DIURETICS-CARBONIC ANHYDRASE INHIBITORS, LOOP DIURETICS, THIAZIDES Effect of mexiletine 1 by hypokalaemia Uncertain Normalize potassium levels before starting mexiletine... 

SOTALOL DIURETICS-CARBONIC ANHYDRASE INHIBITORS, LOOP DIURETICS, THIAZIDES t risk of ventricular arrhythmias, particularly torsades de pointes ventricular tachycardia, caused by sotalol Hypokalaemia, a side-effect of these diuretics, predisposes to arrhythmias during sotalol therapy Normalize potassium levels before starting sotalol in patients already taking these diuretics. When starting these diuretics in patients already taking sotalol, monitor potassium levels eveiy 4-6 weeks until stable... 

CARBONIC ANHYDRASE INHIBITORS BRONCHODILATORS -BETA-2 AGONISTS, THEOPHYLLINE Risk of hypokalaemia Additive effects Monitor blood potassium levels prior to concomitant administration and during therapy. Administer potassium supplements to prevent hypokalaemia... 

CARBONIC ANHYDRASE INHIBITORS CARDIAC GLYCOSIDES Risk of digoxin toxicity t by acetazolamide due to hypokalaemia Uncertain Monitor potassium levels closely. Watch for digoxin toxicity and check levels... 

Phytoplankton particulate matter (organic and biomineralized) contains many trace elements. The most abundant are magnesium, cadmium, iron, calcium, barium, copper, nickel, zinc, and aluminum (Table 1), which are important constituents of enzymes, pigments, and structural materials. Carbonic anhydrase requires zinc or cadmium (Price and Morel, 1990 Lane and Morel, 2000), nitrate reductase requires iron (Geider and LaRoche, 1994), and chlorophyll contains magnesium. Additionally, elements such as sodium, magnesium, phosphorus, chlorine, potassium, and calcium may be present as ions... 

The carbonic anhydrase inhibitors are the most kaliuretic of all diuretics and can cause severe hypokalemia during the first few days of administration. However, hypokalemia is not a problem during long-term administration, because of compensatory potassium retention secondary to acidosis (10). 

Acetazolamide alkaUnizes the urine and increases its volume. Urinary sodium, potassium, and bicarbonate concentrations rise, and chloride concentration falls. These effects are due to inhibition of carbonic anhydrase in the... 

Carbonic anhydrase inhibitors should be used with caution in patients with respiratory acidosis or those with severe loss of respiratory capacity, and in patients with diabetes mellitus. They are contraindicated in patients with hepatic disease or insufficiency, reduced serum concentrations of sodium or potassium, adrenocortical insufficiency, hyperchloremic acidosis, or severe renal disease or dysfunction. They should also be avoided in patients taking salicylates. 

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