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.
Adverse effects 
Mechanism of action 
The potassium-sparing diuretics are competitive antagonists that either compete with aldosterone for intracellular cytoplasmic receptor sites, or directly block sodium channels (specifically epithelial sodium channels (ENaC) by amiloride). 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 antagonists. Those in clinical use include:
- Epithelial sodium channel blockers
- Aldosterone antagonists:
Other Diuretics 
While not classically considered potassium-sparing diuretics, ACE inhibitors (ACEi) and angiotensin receptor blockers (ARB) are hypertensive drugs with diuretic effects that decrease renal excretion of potassium. They work by inhibiting either the production (ACEis) or effects (ARBs) of angiotensin 2. This results in a decrease in aldosterone release, which causes potassium-sparing-diuretic-like effects similar to those of the aldosterone antagonists, spironolactone and eplerenone.
See also 
- "diuretic" at Dorland's Medical Dictionary
- Pharmacology. 2nd ed. Harvey, Champe.
- "ACE INHIBITORS; ARBS/POTASSIUM SPARING DIURETICS". Drug-Drug Interaction. JIRDC. Retrieved 17 March 2012.