Potassium-sparing diuretic
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potassium-sparing diuretics
(K+-sparing diuretics)
A class of mild diuretics that act on the kidneys to promote loss of water. They are different from other diuretics in that they do not cause the loss of potassium ions (thus there is no need for potassium supplements) and they do not worsen diabetes or gout. They are often combined with other types of diuretics to offset or prevent potassium loss in the treatment of hypertension. They are also used (rarely) in the treatment of nephrotic syndrome (a kidney disease characterized by protein loss in the urine and oedema) and oedema that has not responded to other diuretics. The effect of these diuretics lasts for several hours and therefore they should not be taken during the late afternoon or early evening or there may be a need to pass urine during the night. See amiloride hydrochloride; spironolactone; triamterene.
Side effects:
potassium may be retained in the body, causing muscle weakness and abnormal heartbeat. Nausea and gastrointestinal upsets are quite common. For more specific side effects, see entries individual drugs.
Precautions:
potassium-sparing diuretics should be used with great caution in people taking angiotensin-converting enzyme inhibitors, preferably under close medical supervision. They should not be given to people taking potassium supplements. Patients taking potassium-sparing diuretics should be warned not to use potassium-containing salt substitutes as this could lead to high blood concentrations of potassium.
Interactions with other drugs:
angiotensin-converting enzyme inhibitors: increase the risk of severely raised blood concentrations of potassium (see above).
Angiotensin II inhibitors: increase the risk of raised blood concentrations of potassium.
Antihypertensive drugs increase the effect of these diuretics in lowering blood pressure.
Ciclosporin: increases the risk of raised concentrations of potassium.
Lithium its plasma concentration is increased.
| potassium permanganate, potassium iodate, potassium hydroxyquinoline sulphate | |
| povidone, povidone–iodine, pramipexole |
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Potassium-sparing diuretic
Potassium-sparing diuretics are diuretic drugs that do not promote the secretion of potassium into the urine.[1]
They are used as adjunctive therapy, together with other drugs, in the treatment of hypertension and management of congestive heart failure.
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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). The combination therefore helps maintain a normal reference range for potassium.
Adverse effects
On their own this group of drugs may raise potassium levels beyond the normal range, termed hyperkalemia, which risks potentially fatal arrhythmias.
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.[2]
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:
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.[3] They work by inhibiting the 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
References
- ^ "diuretic" at Dorland's Medical Dictionary
- ^ Pharmacology. 2nd ed. Harvey, Champe.
- ^ "ACE INHIBITORS; ARBS/POTASSIUM SPARING DIURETICS". Drug-Drug Interaction. JIRDC. http://www.jirdc.org/Files/Formulary/dd00135.html. Retrieved 17 March 2012.
External links
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