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Drug Comparisons
Diuretics
Every day, about 150 to 200 quarts of blood filter through the kidneys where waste products, excess water, and unnecessary minerals are removed. The fluid passes through a complex system of tubes, called nephrons that are responsible for regulating the balance of water and minerals in the blood. A nephron has several distinct sections that perform specific functions--some sections transport water while others transport certain minerals.
When minerals like sodium (abbreviated as "Na") and potassium (abbreviated as "K") are dissolved in the blood, they are able to carry an electric current. This is why they are known as "electrolytes". Exact amounts of water and electrolytes are needed for the body to function properly. Urine is the vehicle the body uses to rid itself of the excess. On an average day only one or two quarts of urine is produced.
Often called "water pills", diuretics work in the kidneys to increase the elimination of water and electrolytes, thereby causing more urine to form. Because the amount of fluid in the body is lowered, blood pressure goes down, too.
Different types of diuretics work in different areas of the nephron. Four of the most common types or classes of diuretics are:
- Thiazide and Thiazide-like Diuretics
- Loop Diuretics
- Potassium-sparing Diuretics
- Combination Diuretics
Drugs in this Class
Amiloride and Hydrochlorothiazide
Bumetanide Tablets
(
Bumex
)
Chlorothiazide Tablets
Chlorthalidone Tablets
(
Chlorthalidone, Thalitone
)
Furosemide Oral Solution
Furosemide Solution for Injection
Furosemide Tablets
(
Lasix Tablets
)
Hydrochlorothiazide Capsules
(
HCTZ Capsules, Microzide Capsules
)
Hydrochlorothiazide and Triamterene Capsules
(
Dyazide, HCTZ and Triamterene Capsules
)
Indapamide
Metolazone Tablets
(
Zaroxolyn Tablets
)
Spironolactone and Hydrochlorothiazide Tablets
(
Aldactazide Tablets
)
Torsemide Injection
(
Demadex Injection
)
Torsemide Tablets
(
Demadex Tablets
)
Triamterene
(
Dyrenium
)
Summarizing the Evidence
According to current research and national treatment guidelines diuretics are generally the best first step in treating high blood pressure to prevent heart failure (HF). This is especially true for African-Americans. Diuretics are usually the least expensive of the high blood pressure medicines available.
Thiazide and Thiazide-Like Diuretics
Chlorthalidone, Hydrochlorothiazide, Indapamide, and Metolazone
Diuretics in this class are suggested as the first drugs to try for most people with high blood pressure. They affect the part of the nephron called the distal convoluted tubule, where large amounts of sodium and water are absorbed back into the body. By blocking the re-absorption process, these drugs force more sodium and more water into the urine to be removed from the body. Thiazides may also relax the muscles in blood vessel walls, making blood flow more easily. Evidence from clinical trials shows that these diuretics can help decrease death and other complications due to high blood pressure. All thiazide and thiazide-like diuretics are thought to be comparably effective.
Loop Diuretics
Bumetanide, Furosemide, and Torsemide
"Loop" diuretics--so named because they work in the area of the nephron called the "Loop of Henle"-- mainly interfere with the body's re-absorption of chloride, but they also keep sodium from re-entering the blood. Unfortunately, loop diuretics are also more likely to promote the elimination of calcium, magnesium and--especially--potassium. Shortages of any of these essential electrolytes can cause serious problems such as irregular heartbeat, but proper monitoring of these electrolytes can prevent potential complications. It may be necessary to take a potassium supplement while on a loop diuretic to ensure potassium does not become too low. Loop diuretics are generally not as effective as thiazide diuretics for controlling blood pressure because their duration of effect is shorter. This can result in a loss of blood pressure control at times throughout the day when the effects of the loop diuretics wear off. All loop diuretics are thought to be comparably effective.
Potassium-Sparing Diuretics
Amiloride, Spironolactone, Eplerenone, and Triamterene
The third common group of diuretics consists of drugs that are much weaker than the thiazides or the loop diuretics. Even though they do not work quite as well, potassium-sparing diuretics do not reduce potassium levels nearly as much as the loop diuretics do. They are often used in combination with other diuretics. All potassium-sparing diuretics are thought to be comparably effective.
Recent studies have also shown that spironolactone not only reduces blood pressure in persons who have Type 2 diabetes with kidney problems, but it also safely adds a protective effect to the kidneys and heart. Eplerenone is a similar medication to spironolactone but has fewer side effects and is often used in patients that cannot tolerate spironolactone.
Combination Diuretics
Amiloride and Hydrochlorothiazide, Spironolactone and Hydrochlorothiazide, and Triamterene and Hydrochlorothiazide
Since they are not very effective alone, the potassium-sparing diuretics that are used in the U.S. are most often combined into a single tablet or capsule with another diuretic--usually hydrochlorothiazide (many times abbreviated as "HCTZ"). All combination diuretics are thought to be comparably effective.
Finally, the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (the treatment guidelines used by most healthcare providers to guide treatment for high blood pressure) recommends that most patients be treated with a diuretic-based regimen. Diuretics can be used by themselves but many people with hypertension require more than one medication to effectively control their blood pressure. Because of this, diuretics are often put together into a single tablet or capsule with drugs from other classes of antihypertensives. For example, HCTZ has been combined with various ACE inhibitors, beta blockers, and angiotensin receptor blockers (ARBs).
Dosing and Administration
- Thiazide and thiazide-like diuretics are each typically taken once daily.
- The loop diuretics are each typically taken once or twice daily.
- The potassium-sparing diuretics are each typically taken once daily except triamterene which is taken twice daily.
- The combination diuretics are each typically taken once daily except for triamterene and hydrochlorothiazide which can be taken up to twice daily.
Generic Availability
- All diuretics currently available have generic equivalents except eplerenone (Inspra).
Drug Interactions
Some interactions between medications can be more severe than others. The best way for you to avoid harmful interactions is to tell your doctor and/or pharmacist what medications you are currently taking, including any over-the-counter products, vitamins, and herbals. For specific information on how the drugs interact and the severity of the interaction, please use our Drug Interactions Checker.
Side Effects
To view specific side effect information, please use our Side Effect Checker.
Additional Information
References
- Drug Facts and Comparisons. St. Louis, MO. 2007.
- Carter BL, Sassen JJ. Hypertension. In: DiPiro JT, Talbert RL, Yee GC, et al., (Eds). Pharmacotherapy: a pathophysiologic approach. 6th ed. New York: McGraw-Hill, 2005:185-217.
- Chobanian AV, Bakris GL, Black HR, et al. The seventh report of the joint national committee on prevention, detection, evaluation, and treatment of high blood pressure. The JNC 7 Report. JAMA 2003; 289:2560-2572.
- Drugdex Database. In: Gelman CJ, Rumack BH, editors. Denver: Micromedex Inc. 2004.
- American Heart Association. Available at: http://www.americanheart.org/presenter.jhtml?identifier=3039311. Accessed June 16, 2006 and July 19, 2007.
- Rossing K, Schjoedt KJ, Smidt U, et. al. Beneficial effects of adding spironolactone to recommended antihypertensive treatment in diabetic nephropathy: a randomized, double-masked, cross-over study. Diabetes Care. 2005(9):2106-12.
- Padilla MC, Armas-Hernandez MJ, Hernandez RH, Israili ZH, and Valasco M. Update of diuretics in the treatment of hypertension. American Journal of Theraputics. 2007 Mar-Apr; 14(2): 154-60.
- Baguet JP, Robitail S, Boyer L, Devensason D, and Auquier P. A meta-analytical approach to the efficacy of antihypertensive drugs in reducing blood pressure. American Journal of Cardiovascular Drugs. 2005; 5(2): 131-40.
Last Updated: April 2008
This content was created by members of the DrugDigest team of experts and is solely under DrugDigest's editorial control.
Note: The above information is intended to supplement, not substitute for, the expertise and judgment of your physician, pharmacist, or other healthcare professional. It should not be construed to indicate that the use of the product is safe, appropriate, or effective for you. Consult your healthcare professional before taking any medication.
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