Introduction to Diuretics

Diuretics can help lower blood pressure (which can help prevent heart attacks and strokes), and the amount of sodium in the body.

There are four main types of diuretics: thiazide, loop, potassium-sparing, and osmotic diuretics. 

Thiazide diuretics work by blocking the reabsorption of sodium and chloride ions in the distal tubule, which promotes natriuresis (excretion of sodium in the urine) and diuresis (increased urine excretion). This process can help reduce blood pressure.

Loop diuretics work by inhibiting the reabsorption of sodium and chloride ions in the thick ascending limb of Henle’s loop. This causes an increase in urine output which can lead to a reduction in blood pressure.

Potassium-sparing diuretics inhibit aldosterone at its receptor sites on renal tubular cells, which prevents potassium loss during urination but allows sodium excretion to continue normally. This medication is helpful in clients who already have hypokalemia and would be at risk with the other types of diuretics.

Osmotic diuretics increase osmolarity within the filtrate and cause water to move into the lumen of collecting ducts along with sodium chloride ions.

Thiazide Diuretics

Thiazide diuretics, also known as “water pills,” help increase urine output. They increase the amount of sodium and water in the kidneys, resulting in more urine passed out through the ureter and bladder. 

This mechanism of action helps the body get rid of excess fluid, which can lower blood pressure and decrease fluid retention manifested by edema and weight gain. This medication can also increase the excretion of potassium, calcium, and magnesium.

Thiazide diuretics are often prescribed to treat: 

• High blood pressure (hypertension)
• Congestive heart failure
• Fluid retention (associated with congestive heart failure or kidney disease)
• Chronic kidney disease 

Thiazide Mechanism of Action

This medication works by Inhibiting the reabsorption of sodium and chloride ions in the ascending Henle loop and early distal tubule, which promotes natriuresis (excretion of sodium in urine) and diuresis (increased urine excretion).

Thiazide Nursing Interventions

• Monitor symptoms: blood pressure, pulse, intake/output ratios, and daily weight.
• Avoid medication dosage abruptly.
• Encourage increased fluid intake.

Loop Diuretics

Loop diuretics work by blocking sodium reabsorption in the loop of Henle, which is a part of the nephron. This increases sodium and water excretion, causing an increase in urine production.

Loop diuretics are named for their site of action on tubular epithelial cells in the kidney, where they inhibit the absorption of sodium, chloride, and water from the filtrate into the blood.

Loop Diuretics Mechanism of Action

Loop diuretics inhibit the reabsorption of sodium chloride in the proximal and distal convoluted tubules and the loop of henle. This site increases their effectiveness and increases urine output.

Loop Diuretics Nursing Interventions

• Monitor:  blood pressure, pulse, intake/output ratios (I&O), and daily weight.
• Avoid stopping drugs abruptly (unless recommended by a health care provider (HCP).
• Educate clients on avoiding alcohol and non-prescription drugs.

Potassium-Sparing Diuretics

Potassium-sparing diuretics, also known as aldosterone antagonists, are a type of diuretic that blocks the effects of aldosterone on the distal renal tubules. 

This causes more sodium to be excreted in the urine than potassium, which is important for clients who have high blood pressure and other conditions that cause high levels of potassium in their blood. Potassium-sparing diuretics are commonly used to treat high blood pressure and heart failure.

Potassium sparing Mechanism of Action

Potassium sparing diuretics help reduce the excretion of potassium and block the reabsorption of sodium into the kidney. This increased sodium and water in the urine, reducing the excretion of potassium.

Potassium sparing Nursing Interventions

• Monitor blood pressure, pulse, intake/output (I&O) ratios and daily weight.
• Avoid stopping drugs abruptly (unless recommended by a HCP).
• Educate clients on avoiding alcohol and non-prescription drugs.

Osmotic Diuretics

Osmotic diuretics are a class of drugs that increase the production of urine (diuresis). They produce diuresis by increasing the osmotic pressure within the kidney. 

Osmotic Mechanism of Action

Osmotic diuretics increase the density of the filtrate in the glomerulus, preventing selective water reabsorption, and it passes as urine. When osmotic pressure increases, the water is not reabsorbed by the kidney, and it is excreted out of the body, along with sodium and potassium, to some extent. The forced diuresis also helps to reduce pressure inside the brain and eye.

Osmotic Nursing Interventions

• Monitor for serum potassium and electrolyte levels.
• Assess clients for anorexia, muscle weakness, numbness, tingling, paresthesia, confusion, and excessive thirst.

Diuretics Conclusion

Diuretics can help reduce sodium levels in the body and decrease blood pressure, which can help avoid heart attacks and strokes.

Thiazide diuretics prevent the distal tubule’s ability to reabsorb sodium and chloride ions. This increases the amount of water that may be eliminated by urination and lowers blood pressure. 

Loop diuretics function by preventing sodium and chloride ions from being reabsorbed in the thick ascending limb of Henle’s loop. This results in a rise in urine production and a fall in blood pressure.

Potassium-sparing diuretics limit potassium loss during urination while maintaining normal sodium excretion by blocking aldosterone at its receptor sites on renal tubular cells. When hypokalemia is not as severe, these medications can be helpful. 

Osmotic diuretics raise the osmolarity of the filtrate and cause water and sodium chloride ions to migrate into the collecting ducts’ lumen.

Sources

https://www.mayoclinic.org/diseases-conditions/high-blood-pressure/in-depth/diuretics/art-20048129 

https://cjasn.asnjournals.org/content/14/8/1248