- What are diuretics and how do they work?
- For what conditions are diuretics used?
- Are there differences among diuretics?
- What are side effects of diuretics?
- What are the drug interactions of diuretics?
- Examples of diuretics
- Thiazides diuretics
- Loop diuretics
- Potassium sparing diuretics
- Carbonic anhydrase inhibitors
- Osmotic diuretics
- Nonprescription diuretics
For what conditions are diuretics used?
Diuretics also are useful in edema caused by renal dysfunction (for example, nephrotic syndrome, acute glomerulonephritis, and chronic renal failure). Diuretics are used to lower urinary calcium excretion, making them useful in preventing calcium-containing kidney stones.
Thiazide diuretics have off–label (non-FDA-approved) uses for osteoporosis in postmenopausal women. They can be given alone or in combination with calcium or estrogen. Thiazide diuretics also have off-label uses for treating diabetes insipidus.
Are there differences among diuretics?
A major difference among diuretics is the level of potency. Potency variation is due to the differences in the sites of action of diuretics on the kidney structure.
Loop diuretics are the most potent diuretics as they increase the elimination of sodium and chloride by primarily preventing reabsorption of sodium and chloride. The high efficacy of loop diuretics is due to the unique site of action involving the loop of Henle (a portion of the renal tubule) in the kidneys.
Thiazide diuretics increase the elimination of sodium and chloride in approximately equivalent amounts. They do this by inhibiting the reabsorption of sodium and chloride in the distal convoluted tubules in the kidneys.
In the distal tubule, potassium is excreted into the forming urine coupled with the reabsorption of sodium. Potassium-sparing diuretics reduce sodium reabsorption at the distal tubule, thus decreasing potassium secretion. Potassium-sparing diuretics when used alone are rather weak, hence they are used most commonly in combination therapy with thiazide and loop diuretics.
Osmotic diuretics are low-molecular-weight substances that are filtered out of the blood and into the tubules where they are present in high concentrations. They work by preventing the reabsorption of water, sodium and chloride.
What are side effects of diuretics?
When individuals present with fluid imbalance (depletion) due to diuretics, adverse events such as:
- dry mouth,
- muscle pains or cramps,
- muscular fatigue,
- oliguria (decreased or absent production of urine),
- tachycardia, and
- gastrointestinal (GI) disturbances may occur.
Extremely low levels of sodium caused by thiazide diuretics have been associated with death and neurologic damage in elderly patients.
What are the drug interactions of diuretics?
Thiazide diuretics given concurrently with antidiabetic drugs [such as oral agents and insulin Apidra, Exubera, Humulin 70-30, Humalog Mix 50-50, Humalog 75-25, Humulin R, Humulin N, Humulin 50-50, Velosulin, Humalog, Lantus, Levemir, Novolog, Novolog Mix 50/50, Novolog Mix 70/30)] causes a decreased blood level of antidiabetic drugs, hence doses of antidiabetic drugs may need to be increased.
Lithium (Eskalith, Lithobid, Lithonate, Lithotabs) given concurrently with diuretics (thiazides and loop diuretics) may induce lithium toxicity due to decreased renal elimination of lithium. Lithium levels should be monitored to ensure safety.
Potassium-sparing diuretics given with angiotensin converting enzyme (ACE) inhibitors or nonsteroidal anti-inflammatory drugs (NSAIDs) [for example, indomethacin (Indocin)] have been associated with severely elevated levels of potassium (hyperkalemia). Severe hyperkalemia may present as muscle weakness, fatigue and slow heart rate (bradycardia). It is important to monitor potassium blood levels and to have an electrocardiogram performed.
Diuretics are often prescribed with other medications for high blood pressure and heart disease. This may increase the effects of these medications, potentially causing electrolyte abnormalities (such as reduced levels of potassium).
Potassium sparing diuretics
- chlorothiazide [(Diuril) (oral or sodium injection)]
- chlorthalidone (Hygroton)
- indapamide (Lozol)
- hydrochlorothiazide (Hydrodiuril)
- methyclothiazide (Enduron)
- metolazone (Zaroxolyn, Diulo, Mykrox)
- bumetanide (Bumex)
- furosemide [(Lasix) (oral or injection)]
- ethacrynate (Edecrin)
- torsemide [(Demadex) (oral or injection)]
Potassium sparing diuretics
- Amiloride hydrochloride
- spironolactone (Aldactone)
- triamterene (Dyrenium)
- glycerin (Glycerol)
- Mannitol IV
Tova Alladice, M.D.
American Board of Physical Medicine & Rehabilitation