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Thiazide Diuretics Essay

Thiazide diuretics are sulfonamides that contain a thiazide ring. Examples of thiazide diuretics include hydrochlorothiazide and chlorothiazide (Woo & Robinson, 2015). According to Sica, Carter, Cushman & Hamm (2011) thiazides are the most commonly used diuretics and the main role is to inhibit the sodium-chloride symport, and the inhibition takes place in the distal convoluted tubule.

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Mechanism of action

Thiazides are secreted in the proximal convoluted tubules and travel along the nephrons. The distal convoluted tubule is the site of action where they inhibit the sodium-chloride ion symporter found in the distal convoluted tubules’ luminal membrane (Woo & Robinson, 2015). The Na+Clfound in the distal convoluted tubule facilitates the absorption of Na+ from the distal tubules and back into the interstitium. The amount of Na+ reabsorbed through the sodium-chloride symporter approximately 7% of the total sodium reabsorbed (Duarte & Cooper-DeHoff, 2010). The thiazide administered binds to the Cl-binding site leading to the inhibition of the symporter. The inhibition leads to the retention of sodium and chloride ions in the tubule, and these are excreted in urine (Duarte & Cooper-DeHoff, 2010). As this symporter reabsorbs only about 7% of the filtered sodium, the diuretic effect is moderate but sufficient enough to void about 6% TO 7% GFR (Duarte & Cooper-DeHoff, 2010). This, therefore, may increase the flow of urine in as much as three-fold to six-fold such that the patient can pass up to nine liters of urine per day.

The increase in urine loss leads to the reduction of extracellular fluid as well as plasma volume. The loss in volume leads to a diminished venous return coupled with a reduced cardiac output. an increased release of renin and a decrease in blood pressure (Woo & Robinson, 2015). The inhibition of the Na+Clsymporter also leads to the excretion of electrolytes primarily Na+ and Cl and others such as K+ and H+ because the increased retention of Na+ to the collecting duct leads to increased Na+ reabsorption thatraises the lumen-negative transepithelial potential difference (Woo & Robinson, 2015). The ultimate effect is increased secretion of K+ and H+. Thiazide diuretics also enhance the reabsorption of Ca2+ in the distal convoluted tubule due to its inhibiting effect on Na+ entry (Sica, Carter, Cushman & Hamm, 2011). According to Duarte & Cooper-DeHoff (2010), the result is an enhanced activity of the Na+ Ca2+ exchanger in the basolateral membrane of the epithelial cells.

Clinical indications

Thiazide diuretics have several clinical indications. Thiazide diuretics are indicated in hypertensive cases. This is due to their ability to reduce blood pressure as a result of their ability to reduce extracellular fluid and plasma volume (Woo & Robinson, 2015). The effect leads to reduced cardiac output and lowered blood pressure and therefore can be indicated to patients with high blood pressure. Thiazide diuretics are also indicated to treat generalized edemas for instance hepatic, cardiac and renal edema owing to their ability to increase the amount of water lost through urine (Sica, Carter, Cushman & Hamm, 2011). Thiazide diuretics are also indicated in patients suffering from calcium nephrolithiasis and osteoporosis as they help reduce the excretion of calcium ions (Sica, Carter, Cushman & Hamm, 2011). Thiazides are also indicated to treat nephrogenic diabetes insipidus. Since thiazide diuretics reduce the reabsorption of bromide ions and also reduce the reabsorption of calcium ions, they are indicated to treat bromide intoxication.

References: Thiazide Diuretics Essay

Duarte, J. D., & Cooper-DeHoff, R. M. (2010). Mechanisms for blood pressure lowering and metabolic effects of thiazide and thiazide-like diuretics. Expert review of cardiovascular therapy, 8(6), 793-802.

Sica, D. A., Carter, B., Cushman, W., & Hamm, L. (2011).Thiazide and loop diuretics.The Journal of Clinical Hypertension, 13(9), 639-643.

Woo, T. M., & Robinson, M. V. (2015). PharmacotherapeuticsFor Advanced Practice Nurse Prescribers. FA Davis.

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