Diuretics

Definition

Diuretics are drugs that help to reduce the amount of water in the body. They are sometimes called water pills.

Purpose

Diuretics are used to treat the buildup of excess fluid in the body. Medical conditions such as congestive heart failure , liver disease, kidney disease, and hormonal imbalances can cause fluid to accumulate and tissues to swell (edema ). Certain medications can also cause water retention. When there is too much fluid in the body, blood pressure increases and the heart must work harder to pump. Therefore, diuretics are also often the first drug prescribed to treat high blood pressure (hypertension ). They are the least expensive drug that effectively treats hypertension in many people.

When blood enters the kidney, water, waste products, and dissolved charged particles (ions) such as sodium (Na) and potassium (K) are filtered out of the blood and into special tubules in the kidneys. As they travel through these tubules, some water and particles are reabsorbed, and the rest are excreted as urine. In general, diuretics work by increasing the amount of ions and water that are excreted, thus increasing urine output and reducing the fluid load of the body. This, in turn, lowers blood pressure and reduces tissue swelling so that the heart does not have to work as hard.

Diuretics also may be used in surgery to reduce blood pressure and swelling. For example, mannitol, an osmotic diuretic, may be used to reduce swelling in the brain in some neurosurgical procedures.

Description

There are several classes of diuretics. Each class works in a slightly different way, although the end function of all diuretics is to eliminate excess water from the body. The different classes of diuretics include:

• Loop diuretics include bumetanide (Bumex), furosemide (Lasix), torsemide (Cemadex), and ethacrynic acid (Edecrin). They get their name from the loop-shaped part of the kidney tubules (the loop of Henle) where they have their effect.
• Thiazide and thiazide-like diuretics include such commonly used diuretics as hydrochlorothiazide (HydroDIURIL, Esidrix), chlorothiazide (Diuril), and chlorthalidone (Hygroton).
• Potassium-sparing diuretics help the body retain potassium while losing sodium and water. With many diuretics, potassium is lost from the body along with sodium. Too little potassium can cause serious health problems, because potassium plays a critical role in many metabolic functions. Examples of potassium-sparing diuretics are spironolactone (Aldactone), amiloride (Midamor) and triamterene (Dyrenium).
• Osmotic diuretics keep water from being reabsorbed in the kidney. Mannitol, which is given by intravenous drip, is commonly used to reduce cerebral edema (swelling of the brain). Glycerol is also an osmotic diuretic. Osmotic diuretics are used under special circumstances and are not routinely given to control high blood pressure.
• Carbonic anhydrase inhibitors cause water loss through the kidneys by changing the acidity of urine, but their most common use is in treatment of glaucoma, an eye disease caused by increased pressure in the eye. Acetazolamide (Diamox), dichlorphenamide (Daranide), and methazolamide (Nepatazane) are often given by mouth, even though they primarily treat an eye condition.

In addition, some drugs contain combinations of two diuretics. The brands Dyazide and Maxzide, for example, contain the thiazide diuretic hydrochloro-thiazide along with the potassium-sparing diuretic triamterene.

KEY TERMS

Lupus erythematosus —A chronic autoimmune disease that affects the skin, joints, and certain internal organs.

Pancreas —A gland located near the liver, the pancreas produces enzymes and fluids that help to breakdown food. It also produces the hormone insulin that the body must have to utilize sugar (glucose).

Potassium —A mineral found in whole grains, meat, legumes, and some fruits and vegetables. Potassium is important for many body processes, including proper functioning of nerves and muscles.

Triglyceride —A substance formed in the body from the breakdown of fat in the diet. Triglycerides are the main fatty materials in the blood. Triglyceride levels are important in the diagnosis and treatment of many diseases, including high blood pressure, diabetes, and heart disease.

Some nonprescription (over-the-counter, OTC) medicines and herbal remedies also function as diuretics. However, the drugs described here cannot be bought without a physician's prescription. They are available in tablet, capsule, liquid, and injectable forms.

Recommended dosage

The recommended dosage depends on the type of diuretic, the condition it treats, and the individual's size, age, and health. Patients should check with the physician who prescribed the drug or the pharmacist who filled the prescription for the correct dosage and then take the medicine exactly as directed.

Precautions

Seeing a physician regularly while taking a diuretic is important. The physician may order blood work and will do a physical examination to make sure the diuretic is working as it should without unwanted side effects.

For patients taking a class of diuretic that can cause large amounts of potassium to be excreted, physicians may recommend adding potassium-rich foods such as bananas to the diet , and they may suggest taking a daily potassium supplement. If the

physician recommends any of these measures, the patient must make sure to closely follow the directions. The patient should not make other significant diet changes or take any dietary supplements without checking with the physician. People who are taking potassium-sparing diuretics should not add potassium to their diets, as too much potassium may be harmful.

Patients taking potassium-sparing diuretics should know the signs of too much potassium and should check with a physician as soon as possible if any of these symptoms occur, including:

• irregular heartbeat
• breathing problems
• numbness or tingling in the hands, feet, or lips
• confusion or nervousness
• unusual tiredness or weakness
• weak or heavy feeling in the legs

Patients taking diuretics that cause potassium loss should know the signs of too little potassium and should check with a physician as soon as possible if they have any of these symptoms, including:

• fast or irregular heartbeat
• weak pulse
• nausea or vomiting
• dry mouth
• excessive thirst
• muscle cramps or pain
• unusual tiredness or weakness
• mental or mood changes

People who become ill with gastrointestinal diseases while taking diuretics may lose too much water or potassium if they have severe vomiting and diarrhea .

Diuretics drugs make some people feel light-headed, dizzy, or faint when they get up after sitting or lying down. Older people are especially likely to have this problem. Drinking alcohol, exercising, standing for long periods, or being outdoors in hot weather may make the problem worse. To lessen this problem, a person should get up gradually and hold onto something for support if possible. The patient should avoid or limit the amount of alcohol he or she drinks and be careful in hot weather or when exercising or standing for a long time.

People who take a diuretic should tell the health-care professional before having surgical or dental procedures, medical tests, or emergency treatment.

Special conditions

People who have certain medical conditions or who are taking certain other drugs may encounter problems if they take diuretics. Before taking diuretic drugs, they should be sure to let the physician know about these conditions.

ALLERGIES Anyone who has had unusual reactions to diuretics or sulfonamides (sulfa drugs) in the past should let the physician know. The physician should also be told about any allergies to foods, dyes, preservatives, or other substances.

PREGNANCY Diuretics will not help the swelling of hands and feet that some women experience during pregnancy. Pregnant women should not use diuretics unless prescribed by their obstetrician or other physician. Although studies have not been done on pregnant women, studies of laboratory animals show that some diuretics can cause harmful effects when taken during pregnancy.

BREASTFEEDING Some diuretics pass into breast milk, but no reports exist of problems in nursing babies whose mothers use this medicine. However, thiazide diuretics may decrease the flow of breast milk. Women who are breastfeeding and need to use a diuretic should check with the physician.

OTHER MEDICAL CONDITIONS Side effects of some diuretics may be more likely in people who have had a recent heart attack or who have liver disease or severe kidney (renal) disease. Other types of diuretics may not work properly in people with liver disease or kidney disease. Diuretics may worsen certain medical conditions such as gout , kidney stones , pancreatitis, lupus erythematosus, and hearing problems. In addition, people with diabetes should be aware that a diuretic may increase blood sugar levels. People with heart or blood vessel disease should know that some diuretics increase cholesterol or triglyceride levels.

The risk of an allergic reaction to certain diuretics is greater in people with bronchial asthma . Before using diuretics, people with any of these medical conditions should make their physicians aware of their medical history. Also, people who have trouble urinating or who have high blood levels of potassium may not be able to take diuretics and should discuss these conditions with their physician before using them.

Side effects

Some people feel unusually tired when they first start taking diuretics. This effect usually becomes less noticeable over time, as the body adjusts to the medicine. Other side effects, such as loss of appetite, nausea, vomiting, stomach cramps, diarrhea, and dizziness , usually lessen or go away as the body adjusts to the diuretic drug. These problems usually do not need medical attention unless they continue or interfere with normal activities.

Some diuretics make the skin more sensitive to sunlight. Even brief exposure to sun can cause severe sunburn, itching , a rash, redness, or other changes in skin color. While being treated with this medicine, the person should avoid being in direct sunlight; wear a hat and tightly woven clothing that covers the arms and legs; use a sunscreen with a skin protection factor (SPF) of at least 15; protect the lips with a sun-block lipstick; and not use tanning beds, tanning booths, or sunlamps. People with fair skin may need to use a sunscreen with a higher SPF.

Because diuretics increase urine output, people who take this medicine may need to urinate more often, even during the night. Healthcare professionals can help patients schedule their doses to avoid interfering with their sleep or regular activities.

Interactions

Diuretics may interact with other drugs, herbs, or dietary supplements. When this occurs, the effects of one or both of the drugs become either more or less effective or the risk of side effects may increase. Anyone who takes a diuretic should inform the healthcare providers about all other prescription and over-the-counter drugs, herbs, and dietary supplements that he or she is taking in order to avoid harmful interactions.

Some common drugs that may interact with diuretics include:

• Angiotensin-converting enzyme (ACE) inhibitors such as benazepril (Lotensin), captopril (Capoten), and enalapril (Vasotec), which are used to treat high blood pressure. Taking these drugs with potassium-sparing diuretics may cause levels of potassium in the blood to be too high, increasing the chance of side effects.
• Cholesterol-lowering drugs such as cholestyramine (Questran) and colestipol (Colestid). Taking these drugs with combination diuretics such as Dyazide and Maxzide may keep the diuretic from working. The person should take the diuretic at least one hour before or four hours after the cholesterol-lowering drug.
• Cyclosporine (Sandimmune), a drug that suppresses the immune system. Taking this medicine with potassium-sparing diuretics may increase the chance of side effects by causing levels of potassium in the blood to be too high.
• Potassium supplements, other drugs or supplements containing potassium, or salt substitutes that contain potassium. Taking these with potassium-sparing diuretics may lead to too much potassium in the blood, increasing the chance of side effects.
• Lithium, used to treat bipolar disorder (manicdepressive illness). Using this medicine with potassium-sparing diuretics may allow lithium to build up to poisonous levels in the body.
• Digitalis, also called digoxin (Lanoxin) or digitoxin. Using this medicine with combination diuretics such as triamterene-hydrocholorthiazide (Dyazide, Maxzide) increases the chance of irregular heartbeat.

The list above does not include every drug or herb that may interact with diuretics. The patient should check with a physician or pharmacist before combining diuretics with any other prescription or over-the-counter drugs, herbal medicines, or dietary supplements.

Resources

books

Rubin, Alan L. High Blood Pressure for Dummies 2nd ed. Indianapolis, IN: Wiley Pub., 2007.

organizations

American Heart Association. 7272 Greenville Avenue, Dallas, TX 75231. (800) 242-8721. http://www.americanheart.org (accessed March 19, 2008).

other

Anaizi, Nasr. “Diuretics.” The Drug Monitor [cited March 19, 2008]. http://www.thedrugmonitor.com/diuretics.html

“Diuretics.” Mayo Clinic. December 22, 2006 [cited March 19, 2008]. http://www.mayoclinic.com/health/diuretics/HI00030

“Diuretics Key Factor in Preventing Heart Failure."American Heart Association. May 1, 2006 [cited March 19, 2008]. http://www.americanheart.org/presenter.jhtml?identifier=3039311

Nancy Ross-Flanigan

Sam Uretsky PharmD

Tish Davidson A.M.