Introduction
Diuretics Agents or what called (water pills), help rid the body of salt, sodium and water. Most work by making the kidney release more sodium into urine. The sodium then takes water with it from the blood. That reduce the amount of fluid flowing through the blood vessels, which reduces pressure on the vessel walls. Furthermore, doctors prescribe certain diuretics agents to prevent, improve or treat symptoms in different health conditions, for example: heart failure, tissue swelling (edema), liver failure and kidney disorders, such as kidney stones. There are four main classes of diuretics agents including: loop diuretics, thiazide diuretics, carbonic anhydrase inhibitors and potassium sparing diuretics. Loop diuretics considered as the most widely used diuretics for both outpatient therapy of chronic heart failure patients and in patients hospitalized for severe decompensated heart failure, then the thiazide diuretics. Except for aldosterone antagonists, that are used for their mineralocorticoid receptor antagonistic actions instead of as a diuretic Potassium sparing diuretics are used much less often. Carbonic anhydrase inhibitors are the least used.
DISCUSSION
Types of Diuretic Agents
The main difference between diuretic agents is the level of potency. Potency level variation is due to the differences in the sites of action of the agent (Sica, 2012). Selecting the proper use of diuretics in patients with heart failure, nephrotic syndrome, cirrhosis and renal disease requires an understanding of the pathophysiology of these conditions, table(1) below show a summary of most important diuretic agents and the uses of each (Qavi and Hassaan, 2015).
-Loop diuretics
The most commonly used loop diuretic agents in the heart failure management are Furosemide, torsemide, and bumetanide. The absorption rate and metabolism between loop diuretics are different. Loop diuretics are the strongest diuretics because they increase the sodium, chloride and potassium elimination by preventing pumping them in the thick ascending limb of the loop of Henle. (Sica, 2012)
-Thiazide diuretics
Hydrochlorothiazide and metolazone which is a "thiazide-like" diuretic are the most used thiazide agents to treat heart failure. Metolazone is an oral diuretic agent which is a sulfonamide derivative of a thiazide diuretic agent with a same site action. Thiazide diuretic agents almost on the same level they increase the sodium and chloride elimination. By blocking the sodium and chloride transporters, they achieve the sodium and chloride level increment. (Qavi and Hassaan, 2015)
-Potassium-sparing diuretics
The most commonly used potassium-sparing diuretics are amiloride and triamterene these agents have a weak diuretic effects and they are usually combined with loop and thiazide diuretics to promote diuresis. Aldosterone antagonists, eplerenone and spironolactone diuretics are different from amiloride and triamterene because they work as mineralocorticoid receptor blockers, while for amiloride and triamterene diuretics they block the epithelial sodium channel. In general Potassium-sparing diuretics minimize sodium reabsorption in the distal tubule, and that lead to decrease potassium secretion. (Qavi and Hassaan, 2015)
-Carbonic anhydrase inhibitors
The only carbonic anhydrase inhibitor that work with considerable diuretic actions is Acetazolamide. By maximize the sodium, potassium, bicarbonate and water excretion from the renal tubule Carbonic anhydrase inhibitors are work. (Sica, 2012)
Figure 1: Site of action for each type. (Lueder and Atar, 2013)
Table 1 : summary of agents and uses. (Lueder and Atar, 2013)
Uses of Diuretic Agents
Diuretics Agents are commonly used in diseases distinguished by excess extracellular fluid, including renal disease, the nephrotic syndrome, cirrhosis and heart failure.
-Renal Insufficiency
A loop diuretic is the preferred diuretic agents for patients with renal insufficiency. Despite a large dose of a thiazide will cause diuresis for patients with mild renal insufficiency, the response for patients taking a creatinine clearance treatment of less than about 50 ml per minute is weak. A continuous intravenous infusion could be tried for patients who have poor responses for intermittent doses of a loop diuretic. A patient with edema caused by renal insufficiency should be prescribed increasing doses of loop diuretics until a functional dose is identified. The effective dose should be given as needed to preserve the response, depending on to the patient's ability to restrict sodium intake and the duration of effective action of the drug. A thiazide diuretic should be added if the response is inadequate after giving the maximum dose. The only recourse is dialysis if diuresis remains an inadequate. (Lueder and Atar, 2013)
-The Nephrotic Syndrome
Nephrotic syndrome is identified by the presence of proteinuria, edema, hyperlipidemia, and hypoalbuminemia. 3 new cases per 100,000 each year for adults are diagnose of nephrotic syndrome. Besides the treatment of underlying disease, the management of nephrotic syndrome includes limiting proteinuria and promoting diuresis to decrease fluid overload. Creating a negative sodium balance is the key to effective treatment. Patients are asked to control their daily sodium intake (<100 mmol per day; 3g per day), control their fluid intake (1.5 liters per day), along with taking diuretics. The diffusion of diuretics in the extracellular compartment is increasing due to low serum albumin levels. For that, a combination of albumin and diuretic may be needed to achieve sufficient levels of loop diuretic at the active site. An infusion of 25 g of albumin with 30 mg of furosemide might improve the diuresis. (Qavi and Hassaan, 2015)
-Cirrhosis
The often first-line therapy includes sodium limitation to (2000 mg sodium per day). The second line of treatment is both oral diuretics and total abstinence from alcohol. Spironolactone diuretic agent is recommended for a patient with cirrhosis and edema, starting with a dose of 50 mg. Using Spironolactone alone is as effective as when it is combined with furosemide. Also amiloride can be used as an alternative, starting with 5 mg per day and titrating up to 20 mg per day although it is not effective as spironolactone. (Qavi and Hassaan, 2015)
-Heart Failure
The major cause of morbidity among the elderly Americans is Heart failure. The first-line therapy for heart failure patients with congestion is diuretics. A meta-analysis illustrating the benefits of diuretics for chronic heart failure shows a decline in mortality (3 trials, 202 patients) and a decrease in worsening heart failure (2 trials, 169 patients) in patients compared to placebo. Compared to active controls a few clinical trials (4 trials, 169 patients) also demonstrated that diuretics improved exercise indulgence in patients with chronic heart failure. Initially thiazide diuretic are used to manage mild congestive heart failure. However, loop diuretics (e.g., furosemide, torsemide, or bumetanide) are the main drugs used in the treatment process of heart failure. Intense heart failure causes decline in absorption rate of loop diuretics. Intravenous diuretics are considered to be more powerful than oral doses and are used in advanced heart failure. (Lueder and Atar, 2013)
Conclusion
In conclusion, diuretic agents are used for the treatment of many health conditions including: heart failure, cirrhosis, renal insufficiency, and nephrotic syndrome. The difference between all agents is the level of potency and the level of potency differ because of the differences in the sites of action of the agent. According to most published papers loop diuretics are the most commonly used agents among the others. I believe discovering these agents from early times has help the human being for the survival along the centuries.