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). The combination therefore helps maintain a normal reference range for potassium.
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 (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.
Potassium-sparing diuretics do not share any obvious chemical similarities, except for the steroid-structure of the aldosterone antagonists. Those in clinical use include:
- Epithelial sodium channel blockers
- Aldosterone antagonists:
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pt:Diurético poupador do potássio