Potassium sparing diuretics

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Potassium sparing diuretics

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A 49-year-old man comes to his primary care provider for evaluation of gynecomastia, which the patient first noticed two weeks ago. The patient does not have breast tenderness or discharge. Past medical history is notable for hypertension and hyperlipidemia. Two months ago, the patient was started on a new antihypertensive agent that can lead to elevated serum potassium levels as a side effect. Family history is notable for breast cancer in his mother.  The patient consumes around 3-4 beers per week and smokes one pack of cigarettes per day. Temperature is 37.1°C (98.8°F), blood pressure is 130/82 mmHg, and pulse is 76/min. Physical examination is notable for the findings below. Cardiovascular, pulmonary, and abdominal exams are noncontributory. Which of the following best describes the underlying cause of this patient’s symptoms?
 
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External References

First Aid

2024

2023

2022

2021

Adverse effects/events

spironolactone endocrine effects p. 627

Gynecomastia p. 667

spironolactone p. 676

Spironolactone p. 627, 663, 673, 676

for heart failure p. 316

metabolic acidosis p. 610

Transcript

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Diuretics are medications that act on the kidneys to increase production of urine, and to eliminate water, certain metabolic wastes, and electrolytes from the body.

There are 5 main types of diuretics; carbonic anhydrase inhibitors, osmotic diuretics, thiazide and thiazide-like diuretics, loop diuretics,, and last but not least, potassium sparing diuretics - which is the only class of diuretic that retains potassium, rather than wasting it.

Now, the basic unit of the kidney is called a nephron, and each nephron is made up of a glomerulus, which filters the blood. T.

The filtered content then goes through the renal tubule, where excess waste, and molecules, such as ions and water, are removed or filtered through an exchange between the tubule and the peritubular capillaries.

So the renal tubule plays a huge role in secretion and reabsorption of fluid and ions - such as sodium, potassium, chloride, and magnesium - in order to maintain homeostasis - or the balance of fluid and ions in our body.

The renal tubule has a few segments of its own: the proximal convoluted tubule, the U-shaped loop of Henle, with a thin descending, a thin ascending limb, and a thick ascending limb, and finally, the distal convoluted tubule, which empties into the collecting duct, which collects the urine.

Different kinds of diuretics act on different segments of the renal tubule. Now, potassium sparing diuretics act on the cortical collecting tubules. Here, there are principal cells and α-intercalated cells dispersed amongst the tubule cells.

The principal cell has two pumps on the apical surface, an ATP-dependent potassium pump that pushes potassium into the tubule, and an epithelial sodium channel pump, called ENaC for short, that pulls sodium into the cell.

There’s also a Na/K ATPase pump on the basolateral surface that again moves 2 potassium ions into the cell for every 3 sodium ions out.

Now, the alpha intercalated cells mainly get rid of hydrogen ions from the blood, and they use two pumps on their apical surface for this.

Summary

Potassium-sparing diuretics are a type of diuretic that helps eliminate excess sodium and water from the body while retaining potassium at the same time. Examples of potassium-sparing diuretics include spironolactone, amiloride, and triamterene. In combination with other diuretics, potassium-sparing diuretics can be used in the management of hypertension, while preventing hypokalemia. Common side effects of potassium-sparing diuretics include hyperkalemia and metabolic acidosis.

Sources

  1. "Katzung & Trevor's Pharmacology Examination and Board Review,12th Edition" McGraw-Hill Education / Medical (2018)
  2. "Rang and Dale's Pharmacology" Elsevier (2019)
  3. "Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th Edition" McGraw-Hill Education / Medical (2017)
  4. "Diuretic Therapy in Heart Failure – Current Approaches" European Cardiology Review (2015)
  5. "Managing resistant hypertension: focus on mineralocorticoid-receptor antagonists" Vascular Health and Risk Management (2017)