Diuretic agents are a class of drugs that help promote diuresis, which is the increased production of urine. They help the body maintain fluid homeostasis and are often administered to patients with a condition that causes fluid overload.

In this article, we will provide an overview of diuretic agents, their mechanisms of action, and the most common types.

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What are Diuretic Agents?

Diuretic agents are a class of drugs that stimulates urine production, which promotes the excretion of excess water and sodium.

This is useful in patients with hypervolemia, which is a condition where there is too much fluid in the blood. It occurs in conditions such as congestive heart failure (CHF) and pulmonary edema.

Types of Diuretics

There are two primary types of diuretic agents, including:

  1. Loop diuretics
  2. Osmotic diuretics

The specific type of diuretic is classified based on how the drug works to stimulate urine production.

Loop Diuretics

Loop diuretics are the most commonly prescribed type of diuretic. They work by inhibiting the reabsorption of sodium and chloride in the loop of Henle in the kidneys.

This increases the amount of water and salt that is excreted from the body.

Furosemide (Lasix) is the most common type of loop diuretic and is typically administered to patients with hypertension, peripheral edema, CHF, and pulmonary edema.

Osmotic Diuretics

Osmotic diuretics work by drawing water into the urine, which dilutes the concentration of salts and other solutes.

This type of diuretic is typically used in patients with cerebral edema, where there is excessive fluid in the brain. They are also used to treat urinary abnormalities.

Mannitol (Osmitrol) is the most common type of osmotic diuretic and is administered intravenously.

Diuretic Agents Practice Questions:

1. What is the main purpose of diuretics?
They are used to eliminate excess fluid from the body. They help to promote the production of urine.

2. What are the primary goals of diuretics?
Lower blood pressure and rid body of excess interstitial fluid.

3. What is edema?
Swelling caused by abnormal accumulation of fluid in intercellular spaces of the body.

4. What is glomerular filtration?
The mechanism whereby fluid in the blood is filtered across the capillaries of the glomerulus to be eliminated through the renal ducts.

5. What is hypovolemia?
A decrease in total blood volume.

6. What is a common diuretic that we hear most often as a Respiratory Therapist?
Lasix.

7. What is a nephron?
Functional unit of the kidney; responsible for regulation concentration of water and electrolytes; maintaining fluid balance; maintains homeostasis of internal volume; and, each kidney has approximately 2 million of these.

8. What is ototoxicity?
Damage to the hearing or balance functions of the ear caused by drugs or chemicals.

9. What does synergistic mean?
Effect of 2 drugs on an organism is greater than the effect of either drug alone.

10. What is the normal urine output for a person per 24 hours?
50 mL/hour.

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11. What is the nephron composed of?
Glomerulus, proximal tubule, loop of Henle, distal tubule, and collecting duct.

12. What is the osmotic diuretics mechanism of action?
Reduction of reabsorption of H2O and solutes. Fast-acting agent.

13. Where is the osmotic diuretic location?
Primarily on proximal tubule and descending loop of Henle.

14. What are the osmotic diuretic indications?
For cerebral edema in acute emergency care settings and head trauma.

15. What are examples of osmotic diuretics?
Mannitol, Glycerol, and Urea.

16. What is the carbonic anhydrase location?
The luminal membrane of the proximal tubule.

17. What are the indications of loop diuretics?
HTN (hypertension), CHF, ARF, CRF, Ascites, Nephrotic Syndrome, and Hemodynamic Effect (acute vasodilation and decrease blood pressure).

18. Where is the loop diuretics location?
Ascending loop of Henle.

19. What are examples of loop diuretics?
Furosemide (Lasix), Bumetanide (Bumex) and Torsemide (Demadex).

20. What are the indications for thiazide diuretics?
First line for mild HTN, CHF, and idiopathic hypercalciuria.

21. What are potassium-sparing diuretics?
Spironolactone (Aldactone) and Eplerenone (Inspira).

22. What are the indications for potassium-sparing diuretics?
Chronic liver disease, may cause hyperkalemia and given to patients with potassium problems.

23. Where are potassium-sparing diuretics located?
Distal convoluted tubule.

24. What are the adverse effects of diuretics?
Hypovolemia (dizziness, extreme thirst, excessive dryness, decreased urine output, constipation, acid-base disorders), ototoxicity, and glucose changes.

25. What are some special situations where we may not want to use diuretics?
Not recommended during pregnancy or for breastfeeding women. Lasix is effective/least toxic in pediatric practice.

26. What is the primary goal of diuretic therapy?
Lower blood pressure and rid the body of excessive interstitial fluid.

27. What are five major groups of diuretic drugs?
Carbonic anhydrase inhibitors, osmotic, Thiazide, loop, and potassium sparing.

28. What is the osmotic diuretic mechanism of action?
Reduction of reabsorption of water and its solutes found in the descending loop of Henle and prevents passive reabsorption of water.

29. What is Mannitol?
It is an osmotic diuretic. It is non-toxic, freely filtered, nonreabsorbable and non-metabolized. Given for cardiovascular diseases and administered prophylactically for acute renal failure. It can lower ICP if infused.

30. What are the side effects of carbonic anhydrase inhibitors?
Rapid tolerance building, increase bicarb excretion, metabolic acidosis, drowsiness, fatigue, CNS depression, paralysis (pins and needles) and renal stones.

31. What the carbonic anhydrase inhibitor drug names?
Acetazolamide, methazolamide, and dichlorphenamide.

32. What are the loop diuretic mechanisms of action?
Inhibit sodium, potassium and chloride reabsorbed; inhibit in the ascending loop of Henle; “Lock and key” receptor mechanism; and, enhances magnesium and calcium excretion.

33. What are the main indications for loop diuretics?
Hypertension, CHF (left heart failure) and acute and chronic renal failure.

34. What are the side effects of loop diuretics?
Hypokalemia, hyper uremia, metabolic alkalosis and depletion of magnesium.

35. What are the main indications for thiazide diuretics?
Hypertension, CHF, calcium deposit stones, osteoporosis, diabetes insipidus (decrease peripheral vascular resistance, narrow therapeutic margin) and first line treatment for mild hypertension.

36. What are the side effects of thiazide diuretics?
Depletes potassium, increases sodium exchange in chronic renal failure and hyperglycemia.

37. What are the commonly used thiazides?
Hydrochlorothiazide and Chlorothiazide.

38. What are some examples of potassium-sparing diuretic drugs?
Spironolactone (Aldactone) and Eplerenone (Inspra).

39. What are the main indications for potassium-sparing diuretics?
Chronic liver disease, renal artery stenosis, adrenal hyperplasia, CHF and cirrhosis.

40. What are the side effects of potassium-sparing diuretics?
Can increase potassium too much and glucose intolerance for diabetic patients.

41. What are the side effects of any diuretic?
Hypovolemia and acid-base disorders are most common. Hypokalemia and hypocholemia; glucose changes; and, ototoxicity.

42. What conditions might the patient need a diuretic?
ARDS and CLD.

43. How does a diuretic help with edema?
They help get rid of the edema.

44. What part of the kidney is responsible for the majority of sodium reabsorption?
PCT.

45. What is the enzyme is required for the bicarb reabsorption process on the brush border and in cytoplasmic?
Carbonic anhydrase.

46. What drug inhibits carbonic anhydrase in brush border and cytoplasm?
Acetazolamide. It works in the PCT but also inhibits it in all tissues of body.

47. What does carbonic anhydrase do?
It plays an important role in the secretion of CSF and aqueous humor.

48. What is the effect of acetazolamide in the CNS?
Causes acidosis of CSF resulting in hyperventilation that protects against high altitude sickness.

49. What is the major renal effect of acetazolamide?
Bicarbonate excretion, metabolic acidosis results and causes potassium wasting (self-limiting 2-3 days).

50. Why would a loop diuretic cause hypokalemia?
Large amounts of sodium in the lumen may result in significant potassium wasting and excretion of protons.

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51. Why do NSAIDS decrease the efficacy of most diuretics?
Prostaglandins are important in maintaining GFR.

52. What is a random application of loop diuretics?
They can serve as a treatment for severe hypercalcemia.

53. What is an important toxic side effect of loop agents?
Ototoxicity.

54. How do thiazides cause hypercalcemia?
Decreased sodium transport from the lumen into the tubular cell reduces intracellular sodium and promotes sodium/calcium exchange at the basolateral membrane. Increases calcium reabsorption from urine (opposite effect of loop diuretics).

55. What part of the kidney does reabsorption of water occurs under the control of ADH?
Medullary collecting tubule.

56. How do osmotic diuretics work?
Freely filtered at glomerulus, but poorly reabsorbed from tubule. Remain in the lumen and hold water by the osmotic effect.

57. Other than diuresis, what can mannitol is used to do?
Reduce brain volume and intracranial pressure by osmotically extracting water from tissue into blood. Similar effect occurs in the eye.

58. What osmotic diuretic used to treat increased intracranial pressure?
Mannitol.

59. What is nephrocalcinosis?
Disorder in which there is excessive accumulation of calcium in the kidney parenchyma and tubules.

60. Diuretic agents can cause decreased levels of which electrolytes?
Chloride, potassium, and magnesium.

Final Thoughts

Diuretic agents are a class of drugs that help to promote diuresis and are used to treat patients with hypervolemia. There are two primary types of diuretic agents, loop diuretics and osmotic diuretics.

The most common type of diuretic is furosemide (Lasix), which is helpful in treating patients with conditions that cause fluid overload.

Respiratory therapists should be familiar with diuretic agents as they are commonly used in the treatment of patients with lung diseases.

Be sure to check out our guide on beta-2 adrenergic agonists to learn more about drugs that are used in respiratory care. Thanks for reading!

Written by:

John Landry, BS, RRT

John Landry is a registered respiratory therapist from Memphis, TN, and has a bachelor's degree in kinesiology. He enjoys using evidence-based research to help others breathe easier and live a healthier life.

References

  • Rau’s Respiratory Care Pharmacology. 10th ed., Mosby, 2019.
  • Egan’s Fundamentals of Respiratory Care. 12th ed., Mosby, 2020.
  • Arumugham, Vijay. “Therapeutic Uses Of Diuretic Agents – StatPearls – NCBI Bookshelf.” NCBI Bookshelf, 6 June 2020, www.ncbi.nlm.nih.gov/books/NBK557838.

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Medical Disclaimer: The information provided by Respiratory Therapy Zone is for educational and informational purposes only. It should not be used as a substitute for professional medical advice, diagnosis, or treatment. Please consult with a physician with any questions that you may have regarding a medical condition.