Potassium-sparing diuretics are diuretic

Diuretic

A diuretic provides a means of forced diuresis which elevates the rate of urination. There are several categories of diuretics. All diuretics increase the excretion of water from bodies, although each class does so in a distinct way.- Medical uses :...

 drugs that do not promote the secretion of potassium

Potassium

Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...

 into the urine

Urine

Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

.

They are used as adjunctive therapy, together with other drugs, in the treatment of hypertension

Hypertension

Hypertension or high blood pressure is a cardiac chronic medical condition in which the systemic arterial blood pressure is elevated. What that means is that the heart is having to work harder than it should to pump the blood around the body. Blood pressure involves two measurements, systolic and...

 and management of congestive heart failure

Congestive heart failure

Heart failure often called congestive heart failure is generally defined as the inability of the heart to supply sufficient blood flow to meet the needs of the body. Heart failure can cause a number of symptoms including shortness of breath, leg swelling, and exercise intolerance. The condition...

.

Indications

Potassium-sparing diuretics are generally used in combination with other diuretic drugs (e.g. loop diuretics) that would otherwise tend to lower the potassium levels to potentially dangerous low levels (hypokalemia

Hypokalemia

Hypokalemia or hypokalaemia , also hypopotassemia or hypopotassaemia , refers to the condition in which the concentration of potassium in the blood is low...

). The combination therefore helps maintain a normal reference range

Reference ranges for common blood tests

Reference ranges for blood tests are sets of values used by a health professional to interpret a set of medical test results from blood samples....

 for potassium.

Adverse effects

On their own this group of drugs may raise potassium levels beyond the normal range, termed hyperkalemia

Hyperkalemia

Hyperkalemia refers to the condition in which the concentration of the electrolyte potassium in the blood is elevated...

, which risks potentially fatal arrhythmias.

Mechanism of action

The potassium-sparing diuretics are competitive antagonists that compete with aldosterone for intracellular cytoplasmic receptor sites, or by directly blocking sodium channels (specifically ENaC by amiloride

Amiloride

Amiloride is a potassium-sparing diuretic, first approved for use in 1967 , used in the management of hypertension and congestive heart failure. Amiloride was also tested as treatment of cystic fibrosis, but it was revealed inefficient in vivo due to it's short time of action, therefore...

 (ENaC is Epithelial Sodium Channel)). The former prevents the production of proteins that are normally synthesized in reaction to aldosterone. These mediator proteins are not produced, and so stimulation of sodium-potassium exchange sites in the collection tubule does not occur. This prevents sodium re-absorption and potassium and hydrogen ion secretion.

Chemical structure

Potassium-sparing diuretics do not share any obvious chemical similarities, except for the steroid-structure of the aldosterone

Aldosterone

Aldosterone is a hormone that increases the reabsorption of sodium ions and water and the release of potassium in the collecting ducts and distal convoluted tubule of the kidneys' functional unit, the nephron. This increases blood volume and, therefore, increases blood pressure. Drugs that...

 antagonists. Those in clinical use include:

• Epithelial sodium channel
  Epithelial sodium channel
  The epithelial sodium channel is a membrane-bound ion-channel that is permeable for Li+-ions, protons and especially Na+-ions. It is a constitutively active ion-channel...
  
   blockers
  • Amiloride
    Amiloride
    Amiloride is a potassium-sparing diuretic, first approved for use in 1967 , used in the management of hypertension and congestive heart failure. Amiloride was also tested as treatment of cystic fibrosis, but it was revealed inefficient in vivo due to it's short time of action, therefore...
    
    
  • Triamterene
• Aldosterone antagonist
  Aldosterone antagonist
  Aldosterone antagonist refers to diuretic drugs which antagonize the action of aldosterone at mineralocorticoid receptors. This group of drugs is often used as adjunctive therapy, in combination with other drugs, for the management of chronic heart failure...
  
  s:
  • Spironolactone
    Spironolactone
    Spironolactone , commonly referred to as simply spiro, is a diuretic and is used as an antiandrogen.It is a synthetic 17-lactone drug that is a renal competitive aldosterone antagonist in a class of pharmaceuticals called...
    
    
  • Eplerenone
    Eplerenone
    Eplerenone is an aldosterone antagonist used as an adjunct in the management of chronic heart failure. It is similar to the diuretic spironolactone, though it may be more specific for the mineralocorticoid receptor and is specifically marketed for reducing cardiovascular risk in patients...