Diuretics & Urinaries

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By Medifit Education



 diuretics &


Something that promotes the formation of urine by the kidney. All diuretics cause a person to ‘lose water,’ but they do so by diverse means, including inhibiting the kidney’s ability to reabsorb sodium, thus enhancing the loss of sodium and consequently water in the urine (loop diuretic); enhancing the excretion of both sodium and chloride in the urine so that water is excreted with them (thiazide diuretic); or blocking the exchange of sodium for potassium, resulting in excretion of sodium and potassium but relatively little loss of potassium (potassium-sparing diuretic). Some diuretics work by yet other mechanisms, and some have other effects and uses, such as in treating hypertension. Also known as water pill. Substances in food and drinks, such as coffee, tea, and alcoholic beverages, may act as diuretics.



Diuretics are used to treat several conditions in medicine including heart failure, high blood pressure, liver disease and some types of kidney disease. The use of some diuretics is also indicated in cases of overdose or poisoning, to help increase the excretion of certain substances from the patient’s body.

Diuretics are useful in the management of most patients with CKD. They reduce ECF volume; lower blood pressure; potentiate the effects of ACE inhibitors, ARBs, and other antihypertensive agents; and reduce the risk of CVD in CKD. Choice of diuretic agents depends on the level of GFR and need for reduction in ECF volume.



Diuretics are a type of medication used to increase the amount of water released from the body in a patient’s urine. In fact, diuretics are commonly known as ‘water pills.’

Now to explain how diuretics work we are going to take a trip back in time to your 8th grade science class. Remember the term ‘osmosis’? I bet you thought you would never need to use it, but this is exactly the principle upon which kidneys filter and diuretics work. The kidneys reabsorb electrolytes (mainly sodium, potassium and calcium). Due to osmosis, the water naturally follows the electrolytes to establish an equal concentration of solutes on either side of the semipermeable membrane in the kidney. So, what diuretics do is BLOCK the reabsorption of electrolytes. If the electrolytes are not reabsorbed into the body, but stay in the urine, then voila! The water stays in the urine and is excreted as well, thereby, decreasing the amount of overall fluid in a patient.


Types of Diuretics and Examples

There are three main types of diuretics. Each targets a different part of the kidneys and causes increased water excretion.


1.Thiazide diuretics

Thiazides are commonly used to treat high blood pressure (hypertension) and are often the first medication patients are placed on to manage this condition. Thiazide diuretics target the distal tubule of the kidneys preventing them from reabsorbing sodium back into the body; therefore, the sodium is excreted in the urine. And wherever sodium goes, potassium is sure to follow!

Water is drawn out with the electrolytes into the urine. Thus urine output is increased, and the overall blood volume in the patient is decreased. Also, thiazides are the only diuretics to cause widening of the blood vessels (vasodilation), which is why it is so useful in managing hypertension. Some examples of thiazide diuretics include Chlorothiazide (Diuril), Hydrochlorothiazide (Microzide), and Metolazone (Zaroxolyn).


2.Loop diuretics

This type of diuretic is most commonly used in managing heart failure, edema, and kidney disease. A loop diuretic acts similarly to a thiazide, prompting sodium, potassium and therefore water to be excreted in the urine. However, some key differences exist. First, it targets the Loop of Henle in the kidney. Secondly, it is an especially potent diuretic, causing a high volume of urine to be excreted. Some examples of loop diuretics include Furosemide (Lasix) and Torsemide (Demadex).


3.Potassium sparing diuretics

For some patients, loop and thiazide diuretics are dangerous because they cause the patient to lose not only sodium and water in the urine, but potassium too. If a patient’s blood potassium is too low (hypokalemia), it can lead to complications, especially if the patient has an underlying heart condition, or kidney or liver dysfunction. Therefore, potassium sparing diuretics were created. These diuretics cause ONLY sodium and water to be excreted, but keep potassium from following suit. These medications are used to treat patients with heart failure, liver disease, or kidney disease. Some examples of potassium sparing diuretics include Spironolactone (Aldactone) and Triamterene (Dyrenium).


Side Effects of Diuretics

Diuretics have a long history in the medical community and are considered a relatively safe class of medications. Understandably, all diuretics when first started cause the patient to urinate more frequently (especially loop diuretics). However, this side effect usually abates after the patient has been on the medication for several weeks.

In addition, diuretics can also cause:

  • Headaches due to dehydration
  • Lightheadedness especially with rapid position changes
  • Extreme thirst

Since diuretics work by affecting electrolyte reabsorption, they can also cause imbalances in these electrolytes,

By Medifit Education