Millions of Americans have been diagnosed with high blood pressure. Because hypertension is a major risk factor for the development of heart disease, many patients take medications to achieve optimal blood pressure control. Diuretics are drugs that are commonly used to achieve lower blood pressures by promoting the excretion of water from the body. As a result, lower fluid volume within the body produces lower blood pressures. Unfortunately, the loss of water is often accompanied by a depletion of certain electrolytes, CV Pharmacology says.
Furosemide, Torsemide, Bumetanide
In biology, a general rule is that water follows sodium. The tubules located in the kidneys contain transport channels that absorb sodium in exchange for potassium. Because diuretics inhibit these channels, sodium and water stay in the renal tubules and are later excreted from the body in the form of urine. Loop diuretics such as furosemide, torsemide and bumetanide are often used to treat hypertension and heart failure. They produce a diuretic effect by blocking sodium channels in the Loop of Henle. However, there are still sodium and potassium transport channels further down in the renal tubules. Sodium is exchanged at those latter sites for potassium, which can result in low levels of potassium within the body, a condition known as hypokalemia. Many patients using loop diuretics are required to take potassium supplements to maintain appropriate potassium levels within the body, says CV Pharmacology.
Hydrochlorothiazide
The most common thiazide used for diuresis is hydrochlorothiazide. Thiazides exert their diuretic effect by blocking sodium and potassium transport channels in the distal tubule, located further downstream from the Loop of Henle. As with loop diuretics, excess sodium can still be reabsorbed and exchanged for potassium through channels further down in the renal tubules, resulting in potassium loss. Although rare, excess sodium can also be excreted to the point of causing low levels of sodium within the body, a condition known as hyponatremia, says Uptodate.com.
Spironolactone
Spironolactone is often known as a potassium-sparing diuretic. Because it acts by blocking sodium and potassium transport channels near the end of the renal tubule, it prevents the loss of potassium. Without further opportunities for reabsorption and potassium exchange, the excess sodium is then excreted in the urine. Spironolactone is seldom used alone as a diuretic, because water is often significantly reabsorbed by the time it gets to spironolactone's site of action. Spironolactone is primarily used with other diuretics to enhance the diuretic effect and prevent the loss of potassium. Spironolactone can lead to excess sodium loss and hyponatremia, although this is rare.
References
- UpToDate: Diuretic-Induced Hyponatremia
- CV Pharmacology: Diuretics
- "Well Tolerated Spironolactone-Related Hyponatremia," The Journal of Clinical Hypertension. Joel Handler, MD. (Apr. 2008).
