Diuretics and diets - Definition, Description, Functions, Benefits, Precautions, Risks

Definition :

Diuretics are a group of drugs given to help the body eliminate excess fluid through the kidneys in order to treat hypertension (high blood pressure), kidney and liver disorders, glaucoma, congestive heart failure (CHF), and idiopathic intracranial hypertension (pseudotumor cerebri), a condition characterized by increased fluid pressure within the blood vessels supplying the brain.

In addition to prescription diuretics, there are several types of diuretics available in over-the-counter formulations or commonplace beverages.

Purpose :

Diuretics have several purposes in mainstream clinical medicine:

•  To lower blood pressure in people with hypertension.
•  To lower fluid pressure inside the eyeball in patients with glaucoma.
•  To reduce increased cerebrospinal fluid pressure in idiopathic intracranial hypertension.
•  To reduce blood pressure and swelling during surgical procedures.
•  To reduce bloating and discomfort associated with fluid retention in the premenstrual phase of a woman’s monthly cycle. 

The connection between diuretics and dieting is twofold. First, many of the conditions that are treated by administration of prescription diuretics—particularly hypertension, CHF, and idiopathic intracranial hypertension—are more common in obese patients, more difficult to treat in the obese population, or both. Thus weight loss and lifestyle change are commonly recommended to these patients along with prescription diuretics.

The second connection is that many dieters use or abuse diuretics as a means to quick weight loss. Abuse of diuretics frequently coexists with self-induced vomiting and abuse of laxatives in patients with eating disorders. This combination of behaviors is called purging. Purging may occur in some patients with eating disorders as a means to a slender appearance, but it is also common in high school and college athletes participating in such weight-related sports as rowing, wrestling, gymnastics, and long-distance running. Athletes may also abuse diuretics like furosemide (Lasix) in order to mask the fact that they are taking other drugs to enhance performance in competition. People who abuse diuretics may take herbal preparations reported to have diuretic effects or over-the-counter preparations containing caffeine or pamabrom as well as prescription diuretics.

Description :

Prescription diuretics

There are five major types of prescription diuretics.

LOOP DIURETICS. Loop diuretics are the strongest of the prescription diuretics. They take their name from the fact that they work in the ascending limb of the loop of Henle, a structure in the kidney in which magnesium and calcium are ordinarily reabsorbed. By disrupting the reabsorption of these two ions, loop diuretics bring about increased urine production, which in turn lowers blood volume, leading to lowered blood pressure. Loop diuretics also cause the veins to dilate, which lowers blood pressure mechanically. This vasodilation is independent of the drug’s diuretic effect.

Loop diuretics are usually given to treat edema (accumulation of fluid in body tissues) associated with heart failure; cirrhosis of the liver; impaired kidney function or nephrotic syndrome (a condition in which the kidneys leak protein from blood into the urine); hypertension; or severe hypercalcemia (abnormally high levels of calcium in the blood). They are also given together with other drugs to treat edema of the brain or lungs, conditions that require rapid diuresis. Drugs classified as loop diuretics include furosemide (Lasix), bumetanide (Bumex), ethacrynic acid (Edecrin), and torsemide (Demadex).

THIAZIDE DIURETICS. Thiazide diuretics are derived from a chemical called benzothiadi(A)zene. Unlike the loop diuretics, which work in the loop of Henle, thiazide diuretics work in a different structure called the distal convoluted tubule, although they function in a similar way to increase urine production by decreasing the kidney’s reabsorption of sodium and calcium. They are not as strong as loop diuretics and have fewer adverse effects.

Thiazide diuretics are commonly prescribed to manage high blood pressure because they help to dilate blood vessels as well as lower blood volume by increasing urine output. They are also sometimes given to patients with high levels of calcium in the urine to prevent the formation of kidney stones and lower the risk of osteoporosis. They include such drugs as hydrochlorothiazide (HydroDiuril, Esidrix), chlorothiazide (Diachlor, Diuril), and chlorthalidone (Hygroton, Hylidone).

POTASSIUM-SPARING DIURETICS. Potassium-sparing diuretics include such drugs as amiloride (Midamor) and triamterene (Dyrenium). They are usually given together with loop diuretics in treating CHF or high blood pressure to prevent the patient’s potassium level from falling too low. They work by decreasing sodium reabsorption in the collecting tubules of the kidneys. 

There are two formulations that combine the potassium-sparing diuretic triamterene with the thiazide diuretic hydrochlorothiazide in one pill—Maxzide and Dyazide—thus simplifying the patient’s dosage schedule.

OSMOTIC DIURETICS. Osmotic diuretics are substances that cannot be reabsorbed in the kidney and so increase urine volume by osmosis. The most commonly used osmotic diuretic is mannitol, a sugar alcohol or polyol that is also added to sugar-free candies, mouthwashes, and similar products as an artificial sweetener. Mannitol (Osmitrol) is given intravenously to patients with glaucoma to lower fluid pressure inside they eyeball, and to patients with acute kidney failure following cardiovascular surgery.

Until early 2007, high-dose mannitol was recommended as treatment to reduce fluid accumulation inside the skull in cases of head trauma, on the basis of randomized trials conducted by a neurosurgeon in Brazil who committed suicide in 2005. His papers on the use of mannitol in head surgery were called into question in late 2006; neither his former coauthors nor the journal editors who published his studies have been able to verify his data; and the university he claimed as his affiliation has never employed him.

CARBONIC ANHYDRASE INHIBITORS. Carbonic anhydrase inhibitors are a class of diuretics that increase water loss through the kidneys by changing the acidity of urine. Their most common use, however, is to treat glaucoma by lowering the fluid pressure inside the eyeball. The most common diuretic in this group, acetazolamide (Diamox), is also used as an anticonvulsant (drug given to prevent seizures). Other carbonic anhydrase inhibitors include dichlorphenamide (Daranide) and methazolamide (Neptazane).

Nonprescription diuretics

Nonprescription diuretics are often used by dieters to flush water from the body in the belief that this practice will promote rapid weight loss. According to the Centers for Disease Control and Prevention (CDC), 1% of adult male dieters in the United States and 2% of adult women have used over-the-counter diuretics as part of weight loss attempts.

CAFFEINE. Caffeine is a xanthine alkaloid found naturally in coffee beans, tea leaves, kola nuts, cocoa beans, and a few other plants. It is well known as a central nervous system (CNS) stimulant, enjoyed in brewed coffee, tea, hot chocolate, cola beverages, and energy drinks. It is also available in tablet form as an over-the-counter stimulant in such compounds as NoDoz. Caffeine is broken down in the liver to three substances, one of which is theobromine, which acts as a diuretic and increases urine volume. Some dieters drink coffee as much for its diuretic effects as for its effectiveness is counteracting the fatigue that often accompanies low-calorie diets.

HERBAL PREPARATIONS. Naturopaths and other practitioners of alternative medicine often recommend certain herbal preparations, including herbal teas, as diuretics available without a prescription. Herbs commonly recommended for their diuretic qualities include uva ursi, dandelion, hydrangea, parsley, butcher’s broom, buchu, juniper, horsetail, buckthorn, and asparagus.

ALCOHOL. Beverage alcohol (ethanol) is known to have a diuretic effect; in fact, many of the symptoms of an alcohol hangover, such as headache, nausea, and diarrhea, are related to the dehydration resulting from alcohol intoxication. Many weight-reduction diets (the Mediterranean diet being a notable exception) forbid alcohol because it contains more calories than most people realize—7 calories per gram, in comparison to 9 calories per gram for fat and 4 calories per gram for protein. Some women, however, drink an occasional glass of wine or beer for its diuretic effect, to relieve the discomfort of fluid retention before the onset of their menstrual period.

PAMABROM. Pamabrom is a mild diuretic related chemically to theophylline, one of the breakdown products of caffeine. It is compounded with acetaminophen in a number of over-the-counter (OTC) remedies for premenstrual bloating and backache associated with fluid retention, including New Tylenol for Women, Backaid, and Diurex.

Precautions :

Both prescription and nonprescription diuretics should be used with care.

Prescription diuretics

Prescription diuretics should be used only under a doctor’s supervision and monitored in long-term users, as dosage requirements may change or the doctor may recommend dietary supplements to compensate for electrolytes and nutrients lost through the use of some diuretics. In addition, patients should not stop taking prescription diuretics or change the dosage without consulting their doctor.

•  Loop diuretics. Patients taking loop diuretics may require supplemental potassium, folic acid, and vitamin B1. In addition, they should learn to recognize the symptoms of potassium depletion, as loss of potassium is a common adverse effect of this type of diuretic.
•  Thiazide diuretics. Nursing mothers should not use thiazide diuretics during the first month of breastfeeding, as they can pass into the milk and in some cases decrease the flow of milk. Thiazide diuretics should also be taken with food or milk to lower the risk of upset stomach. They should be used very cautiously in patients with diabetes, as they tend to raise blood sugar levels.
•  Potassium-sparing diuretics. Patients should avoid the use of salt substitutes containing potassium while taking this type of diuretic, as it may lead to overly high levels of potassium in the blood. In addition, patients should be advised to avoid driving or operating dangerous machinery until they know how these drugs affect them, because potassium-sparing diuretics may cause dizziness and blurred vision.
•  Osmotic diuretics. Sodium levels in the patient’s blood should be closely monitored, particularly if the patient develops muscle cramps.
•  Carbonic anhydrase inhibitors. Acetazolamide should not be given to patients with a history of liver or kidney disorders, Addison’s disease, known sensitivity to sulfonamide drugs, or angle-closure glaucoma; and used cautiously in patients with diabetes or gout. The patient should be advised to take this type of diuretic in the morning to prevent sleep interruption.

Nonprescription diuretics

Nonprescription diuretics can still cause adverse effects even though they are weaker than prescription

diuretics:

•  Caffeine. A dose of caffeine higher than 400 milligrams (more than 3 or 4 cups of brewed coffee) will produce a state of caffeine intoxication in most adults. Over-the-counter caffeine tablets, however, typically contain more caffeine than brewed coffee, usually 100–200 mg per tablet. In very high doses (around 5 g), caffeine will produce nausea, coma, convulsions, and eventually death.
•  Herbal preparations. Herbal preparations should be purchased only from reliable sources, as their potency may vary from batch to batch. In addition, herbal products made outside the United States may be adulterated with filler products or contaminated by industrial byproducts.
•  Alcohol. Alcohol should always be consumed in moderation and never combined with driving or operating heavy machinery.
•  Pamabrom. Pamabrom is a mild diuretic that causes skin rashes in a few people who take it for backache or menstrual cramps.

Interactions :

Prescription diuretics interact with some other prescription drugs as well as with herbal products:

•  Loop diuretics. Loop diuretics are known to interact with licorice, digitalis, and buckthorn or alder buckthorn.
•  Thiazide diuretics. Thiazide diuretics interact with insulin to inhibit its effects in lowering blood sugar; they intensify the toxic side effects of lithium therapy; and they increase the effects of corticosteroids in causing loss of potassium.
•  Potassium-sparing diuretics. May increase the toxicity of lithium.
•  Osmotic diuretics. None reported as of 2007.
•  Carbonic anhydrase inhibitors. Enhance the effects of amphetamines and tricyclic antidepressants; increase the excretion of lithium and phenobarbital; increase the risk of aspirin toxicity for patients taking aspirin or other salicylates.

Nonprescription diuretics

Nonprescription diuretics, particularly alcohol, may interact with a variety of substances:

•  Caffeine. Caffeine is known to intensify the effects of cimetidine (a drug that lowers the secretion of stomach acid) and theophylline.
•  Herbal preparations. Herbal preparations with diuretic effects should be strictly avoided by people taking prescription diuretics, as the herbs may intensify the effects of the prescription drugs and lead to various cardiovascular side effects.
•  Alcohol. Alcohol is known to interact with a wide number of prescription medications. It should never be taken together with other drugs that depress the central nervous system. These types of medications include antidepressants, benzodiazepines (tranquilizers), barbiturates, other sleeping medications, narcotic pain relievers (codeine and other derivatives of opium), and antihistamines. Alcohol may interact with antipsychotic medications to cause liver damage, with aspirin to cause stomach bleeding, and with some cardiovascular medications to cause dizziness and fainting.
•  Pamabrom. No interactions between pamabrom and other medications have been reported as of 2007.

Aftercare :

Aftercare following abuse of diuretics varies according to the substance and the consumption pattern. Caffeine intoxication can usually be treated by tapering intake of caffeinated beverages and/or discontinuing use of caffeine tablets. Alcohol hangovers may require rehydration as well as administration of vitamin B6. Abuse of diuretics in patients with eating disorders requires long-term medical nutrition therapy supervised by a professional nutritionist. The position statement of the American Dietetic Association (ADA) is as follows: ‘‘It is the position of the American Dietetic Association (ADA) that nutrition education and nutrition intervention by a registered dietitian is an essential component of the team treatment of patients with anorexia nervosa, bulimia nervosa, and eating disorders not otherwise specified (EDNOS) during assessment and treatment across the continuum of care.’’ Similarly, adolescents who abuse diuretics as part of athletic training regimens require supervision by a registered dietitian as well as by a specialist in sports medicine.

Complications :

Prescription diuretics have a number of side effects:

•  Loop diuretics. Loop diuretics may produce several different types of adverse reactions. The first type are related to diuresis and electrolyte balance. Loop diuretics may cause loss of potassium and magnesium from the body; the loss of magnesium may lead to the loss of additional potassium. Patients taking loop diuretics should be taught to recognize the signs of potassium deficiency (hypokalemia), which include weakness, loss of appetite, irregular heartbeat, constipation, muscle cramps, a weak or heavy feeling in the legs, mental confusion, or unusual tiredness. The second type of adverse reaction to loop diuretics is ototoxicity, or damage to the nerves in the ears that control hearing and the sense of balance. Symptoms of ototoxicity include ringing in the ears (tinnitus) and dizziness. The third type of adverse effect of loop diuretics is uncommon but may occur in patients who are also taking ACE inhibitors (medications to control blood pressure) and nonsteroidal anti-inflammatory drugs (NSAIDs). This so-called ‘‘triple whammy’’ may lead to kidney failure.
•  Thiazide diuretics. Thiazide diuretics may cause low blood potassium levels, impotence in men, and increased levels of blood cholesterol. They also cause photosensitivity in some people, which means that the person will be more sensitive to sunlight and sunburn more readily. Last, thiazide diuretics can raise the levels of glucose and uric acid in the blood, which increases the patient’s risk of developing gout.
•  Potassium-sparing diuretics. Adverse effects may include loss of interest in sex (in both men and women), visual disturbances and dizziness, shortness of breath, nausea and vomiting.
•  Osmotic diuretics. Use of mannitol causes high blood pressure, blurred vision, chills, fever, nausea, and vomiting in some patients.
•  Carbonic anhydrase inhibitors. May depress the activity of bone marrow, leading to anemia; may contribute to liver dysfunction; increases the patient’s risk of developing gut; may lead to overly low blood levels of sodium, potassium, magnesium, and calcium.

Nonprescription diuretics

Adverse effects from nonprescription diuretics may include:

•  Caffeine. Adverse effects from high doses of caffeine include nervousness, insomnia, restlessness, twitching, tingling or flushing of the face, nausea or vomiting, diarrhea, and dehydration.
•  Herbal preparations. Herbal preparations used as diuretics have a wide range of potential adverse effects, ranging from intensifying the effects of prescription diuretics to indigestion, skin rashes, headache, and diarrhea.
•  Alcohol. Complications associated with ethanol consumption include the risks of dehydration and electrolyte imbalance caused by intoxication; alcohol abuse; trauma from alcohol-related accidents; and interactions with other medications.
•  Pamabrom. Pamabrom has been reported to cause skin rashes and dependence in a very small minority of patients.

Parental concerns :

Parents do not ordinarily need to be concerned about children or adolescents abusing prescription diuretics, as these drugs do not produce mood alteration or relieve pain. Adolescents, however, are likely to abuse nonprescription diuretics in relation to eating disorders or athletic competition; one study found that 64% of adolescents diagnosed with eating disorders were using herbal diuretics. A few adolescents may develop caffeine-related disorders apart from eating disorders or sports.

Eating disorders

Abuse of over-the-counter diuretics is common among adolescents with eating disorders accompanied by purging, although it is slightly less common than self-induced vomiting or abuse of laxatives. Although eating disorders are classified as mental health problems, they can have serious lifelong digestive and nutritional consequences, including erosion of tooth enamel, loss of bone density leading to eventual osteoporosis, and ongoing problems with water retention.

Athletic competition

Numerous reports of diuretic abuse among athletes in high school and college sports programs have accumulated since the late 1980s. Abuse of OTC diuretics is higher among both males and females in such weight-related sports as wrestling and rowing than among participants in sports that do not classify athletes by weight (distance running, swimming, basket ball, etc.). More males than females abuse diuretics at both the high school and college levels; the average age of initial misuse of diuretics in one sample was 15.6 years for males and 16.2 years for females. Abuse of diuretics puts young athletes, particularly males, at risk of dehydration, chest pains, fainting, and irregular heart rhythms, particularly when combined with ephedrine or other stimulants.

Caffeine dependence and intoxication

According to DSM-IV, caffeine use typically begins in the mid-teens in the United States and Canada, with levels of consumption increasing into the early adult years (20s and 30s). Among teenagers, caffeine use is usually higher among boys than girls, and higher among smokers than nonsmokers. Most fatal cases of caffeine overdose occur among adults in their early 20s, usually as a result of taking OTC caffeine tablets by mouth or inhaling crushed tablets.